After a career of cracking cold cases, investigator Paul Holes opens up

DAVE DAVIES, HOST:

This is FRESH AIR. I'm Dave Davies, in today for Terry Gross. Network television has given us plenty of fictional crime scene investigators over the years, applying science experience and moxie to track down bad guys from clues they leave behind. Our guest today, Paul Holes, is the real thing. He spent a career investigating crimes in California, specializing in cold cases. He played a critical role in identifying one of the most notorious serial predators in American history, the so-called Golden State Killer, who has admitted to committing 13 murders and 50 rapes in the 1970s and '80s. In a new book, Holes writes about that case and others, and about the day-to-day work of examining gruesome crime scenes, analyzing evidence, and speaking to survivors of horrific crimes and relatives of those who didn't survive. He also writes about the emotional toll the work takes. He's experienced nightmares, panic attacks and marital issues, and says he's used plenty of bourbon to self-medicate.

Since retiring from government work in 2018, he's continued to assist investigators and families as a private citizen, and he's become a celebrated figure in the true crime world. He's appeared in the TV series "America's Most Wanted" and "The DNA Of Murder With Paul Holes," and he co-hosted a podcast called "The Murder Squad." This fall, he'll be co-hosting a new podcast with Kate Winkler Dawson about historic crimes. It's titled "Buried Bones." His new book is "Unmasked: My Life Solving America's Cold Cases."

Paul Holes, welcome to FRESH AIR.

PAUL HOLES: Thank you for having me.

DAVIES: You know, I think we should begin by just telling our listeners that we are going to be talking about some horrific crimes on the show today. And while we won't be giving graphic descriptions of crimes or crime scenes, we will be talking about cases that involve murders and sexual assaults. So it may not be appropriate for all listeners. Paul, I want to start with a scene that's kind of at the end of the story of this quest for the Golden State Killer. And this is at a point when you and other investigators have identified the guy you think is going to be him, a 72-year-old guy named Joe DeAngelo. You're nearing retirement from government service. And you do an unusual thing. You take a visit to his house when he has so far had no contact with investigators. Tell us why you went. What happened?

HOLES: Well, after 24 years of pursuing this Golden State Killer, utilizing new technology, this genetic genealogy technology, about a week prior, I had been made aware that this Joseph DeAngelo was possibly related to the Golden State Killer. And after investigating him for a week and realizing I was going to be retiring the following week, I decided he was a prime suspect. And every time I had a prime suspect in this case, I have to go see, where are they living? What are they driving? What is the neighborhood they're living in like? And so on a Monday, I drove up to Citrus Heights, Calif., which is in the Sacramento area, and parked in front of his house. His car was in the driveway. I knew he was home. But I've been here with prime suspects before. Was he really the guy? And so I started debating, well, I'm retiring tomorrow - or actually just turning my badge and gun in the next day. I'm not sure he really is the Golden State Killer.

So I started to debate. Should I just go knock on this guy's door? He's a former law enforcement officer. Maybe I can establish a bond saying, hey, you're a former cop and you understand how this goes. I'm looking into an old case, you know, chuckle, chuckle. And, you know, let's just get this over with. Give me a sample of DNA, and you'll never be contacted by an investigator on this case again if you're not the guy. But as I sat there, I realized the various aspects that led him to become a prime suspect I could not dismiss. And I didn't want to blow the case, the case that was my passion for a quarter century at that point. And I decided I probably should let things lie. And I drove off.

DAVIES: Yeah, he would be arrested later. I wondered, did you talk to other investigators that you'd worked with on the case about driving up there? Did you tell them what you'd done?

HOLES: No, not at that point. You know, I generally, over the course of my career, I worked my cases alone. I very much was a lone wolf. And once I decided that Joseph DeAngelo was interesting enough to receive my full attention, I just made an independent decision to drive up there. And, you know, in hindsight, this was foolish from an officer safety standpoint, because if I had gone up and knocked on his door, if he recognized me or decided he did not want to be caught, things could have gone very bad for me. He's very proficient with a firearm. He possibly could have been armed with a firearm when he opened the door. And I would have been a sitting duck. So fortunately, I didn't go up to the door, but also, you know, was somewhat foolish and just doing what I typically did, you know, by myself, no radio contact with dispatch. I'm just going out there and I'm trying to work a case.

DAVIES: In the movies, you would have knocked on the door. It's a good thing you didn't.

HOLES: (Laughter).

DAVIES: You write about a time - like, this is in the 1990s. And, you know, the Golden State Killer had originally been a rapist operating in the Bay Area. And those crimes dated back almost two decades. You are in the library. You would like to read stuff in the library there at the crime lab. And you come across this old file cabinet with these dusty folders, each marked EAR. This was a fateful moment for you to pick those up. What did the EAR mean? What were they?

HOLES: Well, you know, this was just such a fortuitous moment in my career because I had just finished reading a book called "Sexual Homicide: Patterns And Motives" by John Douglas, Bob Ressler and Dr. Ann Burgess. This is the academic text that the Netflix show "Mindhunter" is based on. So I just became fascinated with the serial predator and the psychology of the serial predator. So when I open that file cabinet up and I'm seeing this red EAR and starting to flip through these files, I'm recognizing, oh, this is a serial rapist, and that EAR stood for East Area Rapist. This is an offender that actually started up in Sacramento in mid-1976 and was attacking all over the east area of Sacramento, Citrus Heights, Rancho Cordova, et cetera. So that's how this rapist got his moniker.

But then in mid-'78, he moved down to the East Bay into my jurisdiction, and those were the files that I was looking at. And I was hooked because as I read the victim's statements about what this offender was doing to them, what he was saying to them, the fact that he was going into the middle of the night and attacking couples, a man and a woman, I recognized that the psychology of this offender was very different than the typical serial rapist. This was a much bolder and more brazen offender than what I had even read in the "Sexual Homicide" book.

DAVIES: The series of rapes ended in the 1970s. By the time you looked in, it was almost 20 years later. And as you talked to these victims, did the fact that he was never caught still weigh on them? Did they still fear that he might return?

HOLES: Oh, that was a huge fear for some of these victims. You know, I had several women that - I had one woman who went to a vacation house. She had a cabin up in the foothills. And the thermostat was set different than what she remembered setting it when they had previously left. And she calls me. And it's nighttime. And she's saying, I think he's been here. You know, so she's constantly thinking that this guy is going to come back. I had another woman who, after hearing about a potential suspect in Sacramento, and he was still out and about, she moved to Mexico. She wanted to get away because she thought he would come back. These victims - after he left, they continued to be traumatized by the thought that he was still out there. And the East Area Rapist played on that because he would call some of these victims - sometimes years later - to let them know he was still around.

DAVIES: So the East Area Rapist had committed, you know, dozens of rapes in the Bay Area and in the Sacramento area. And there were these murders in Southern California that nobody had connected, really. You played a role here. How did you figure out it was the same person?

HOLES: Well, I had a DNA profile from three cases in Contra Costa County. And talking with Lt. Larry Crompton, he pointed me down to Santa Barbara. And then, eventually, I'm now talking with Orange County Sheriff's lab, who had a DNA profile from two homicides. And in '97, we had different technologies. But I told that DNA analyst, I'm going to be coming back to you once I get caught up on my side with technology. Four years later, my lab is finally caught up. And now, I have updated DNA profiles that are then compared with those profiles down in Orange County, and they matched. Now, in March of 2001, I knew that the East Area Rapist in Northern California was the guy that they knew as the Original Night Stalker, who had killed 10 people between 1979 and 1986 after he had left Northern California.

DAVIES: Wow. That was a huge connection. And it was big news at the time, wasn't it?

HOLES: It was big news. Newspaper articles were written. And, in fact, one of the victims who had been attacked in 1977, the day after The Sacramento Bee published an article, she was called by the East Area Rapist. And he said, remember when we played? He tracked her down 24 years later.

DAVIES: Let me reintroduce you. We're going to take a break here. We're speaking with Paul Holes. He is a retired cold case investigator who still assists families and law enforcement. His new memoir is called "Unmasked: My Life Solving America's Cold Cases." We'll continue our conversation in just a moment. This is FRESH AIR.

(SOUNDBITE OF DANILO PEREZ AND CLAUS OGERMAN'S "RAYS AND SHADOWS")

DAVIES: This is FRESH AIR, and we're speaking with Paul Holes. He spent more than two decades as a criminal investigator in California. He played a critical role in the identification and arrest of the so-called Golden State Killer. His new book is "Unmasked: My Life Solving America's Cold Cases."

You know, while you were working in northern California in Contra Costa County - and you were kind of, in your spare time, in a way, looking at this old cold case of this rapist who eventually we learned was also a serial murderer in Southern California - you were also working on a lot of other cases that involved going to some very grisly crime scenes. And in the book, you describe a lot of them in detail. How did this affect you emotionally?

HOLES: Well, you know, at the time, I didn't realize how these cases were having an impact on me. You know, of course, you know, when you see what some of these offenders do to absolutely innocent victims, it is shocking at first. But then you kind of bury that. And that's what I did, is I buried that shock. And now I'm in the mode of I've got work to do. And, you know, when I'm working on, let's say, a homicide of a child and I'm looking at this child laying there but then see the toys in the room, see photos of this child enjoying life, that ends up weighing on me. And when I would go home in the evenings and I would have similar-aged children in my house - I had two kids at this point - you can't - I couldn't separate that. You know, that's where the work starts to overlay on the personal life.

But, you know, you can't show weakness. I could not show weakness in the law enforcement setting. I had to be able to stay focused in order to do the job, and I would just bury that type of emotional trauma. And I did that throughout the course of my career. And it really wasn't until after I retired - and I just had this psychological meltdown. And ultimately, I went in to see a therapist, and I, you know, talked about my experiences during my career. And that therapist said, Paul, you got to understand. Every time you buried that emotional trauma from these cases, which was many cases, you know, those are little nicks that you get. And now you have so many nicks, you're bleeding out emotionally. And I - you know, I didn't recognize that over the course of my career. But it is - I will tell you, it's very real, and a lot of other people are experiencing that.

DAVIES: I guess the other thing we should talk about is the effect on your marriages. I mean, you - your first marriage ended - with your wife, Lori - and you write about how the job certainly was a major factor here. And a part of it, I'm sure, was the trauma, the emotional trauma that you suffered, which made it - you said - I guess you felt emotionally exhausted and didn't quite have what it was you need to connect with them emotionally. But the other thing is simply the amount of time that you spent obsessively working on these investigations. In some cases, the cold cases, they weren't - you know, they were kind of side projects for you. And so you would be up at night with your laptop. I'm wondering - I don't know. Looking back on it, if you had, you know, maybe not quite spent so many hours, would it have made a difference? What's your take on it?

HOLES: Yeah, well, that is hard to say. And I think, you know, it really underscores what turned out to be the fundamental reason why I wrote this book, is, you know, initially, I thought, OK, I'm going to write the book on the investigation into the Golden State killer and then, ultimately, expand it to all - I've got all these other fascinating cases that I've worked on. But as I was assessing myself and my relationships, I recognized that this became sort of the fundamental message to the reader is that, yes, you know, this profession, working these cases, the obsession that you mentioned, it impacts people that are involved in the profession. It impacted my marriage to Lori, the number of call-outs and then my obsessive aspect. Imagine if you had a loved one killed or a child that went missing and you're checking with law enforcement and the detective assigned that case, you know, he went home for the day, 5 o'clock. He's no longer working on your loved one's cases.

I always felt an obligation. I need to work these cases continuously. So this is where, you know, the message with "Unmasked" is not only talking about the pursuit of the Golden State Killer and these other cases I was involved with, it's really trying to convey that, you know, this profession has an impact on the individuals working it, their sacrifices these individuals have made of themselves, of their families. And that turns out - really is why this book exists. It's now the fundamental message that I want to get out there.

DAVIES: So let's return to the case of the Golden State Killer. I mean, by 2001, you had managed to determine through DNA matching that the same person who had raped 50 women in Northern California was responsible for many murders in Southern California. This was at a time when you were kind of moving up in management in the county investigative offices there in Contra Costa County. You somehow found time to work on this. One of the things you did, you write, is that you went to the scenes of both the killings and the rapes. What was the point there? I mean, investigators had been there. You'd seen the case files. What were you doing?

HOLES: Part of it is just understanding - the geographic spread was huge. You know, the moniker Golden State Killer is so apt because he really was moving around, you know, hundreds of miles between cases. So that was informative. But also looking at the neighborhoods where he's attacking, it helped inform me about, you know, his tactics on how he's approaching a particular house, how he's leaving that house, how he's prowling through a neighborhood. Why is he choosing that certain - that type of neighborhood? One of the most informative aspects that I saw as I was visiting these neighborhoods was he wasn't attacking in lower income areas at all. He was often attacking in upper-middle to even what I would consider, you know, close to upper-class neighborhoods.

And, you know, a lot of the early investigation really focused in on sort of the - what I call the troll under the bridge offender, you know, this homeless, you know, sexual deviant that's driving a beater car. And as I'm looking at these neighborhoods going, if somebody like that showed up in this type of neighborhood, he would stand out. And so that's when I started to get insight as to who my offender could be, going he blends in with the people who live in these types of neighborhoods.

DAVIES: Can you think of a moment when you were at a location and you said saw something that planted a seed in your mind that turned into something fruitful?

HOLES: Oh, there's multiple moments. I think one of the aspects that stands out is down with the double homicide of Keith and Patrice Harrington that occurred in Laguna Niguel down there at what is now known as Dana Point in the southern part of Orange County, right on the coast. It's almost an oceanfront type of community. But this was an upper-scale neighborhood at the time. It still is today. It is gated. It has security guards that work the gate. It has roving security. And as I'm driving around this neighborhood, the question is, well, why here? He's elevating his risk to attack here when he could have gone right across the street and attacked in a community that didn't have security.

So now that starts to make me question, well, maybe he's attacking in this neighborhood because he's already chosen these victims. Well, when did he choose these victims? That becomes the - kind of the driving question of that investigation. Did he choose these victims because he ran into them somewhere else? Who are these victims? Victimology is huge. You know, so it's now diving into who they are and where he potentially could have interacted with them and seen where they lived. So that is where now I'm starting to think, OK, now he's choosing victims from outside of - he's not just prowling neighborhoods and attacking when he sees an opportunity. He's possibly choosing victims elsewhere or had an interaction where he made a decision they're going to become victims and then assesses where they live to make sure that he can actually accomplish the crime and get away with it.

DAVIES: Let me reintroduce you. We're going to take another break here. We are speaking with Paul Holes. He's a retired cold case investigator. His new book is "Unmasked: My Life Solving America's Cold Cases." We'll talk more after this break. This is FRESH AIR.

(SOUNDBITE OF MUSIC)

DAVIES: This is FRESH AIR. I'm Dave Davies, in for Terry Gross. Our guest is Paul Holes, who spent more than two decades as a criminal investigator for the Contra Costa County, California, Sheriff's Office and the district attorney's office. He played a critical role in the identification and arrest of the so-called Golden State Killer responsible for at least 13 murders and 50 rapes in the 1970s and '80s. Holes' new book is called "Unmasked: My Life Solving America's Cold Cases."

You write how you spent a lot of time on this, in some cases, had some suspects you were pretty confident about. Then, ultimately, they were ruled out by DNA testing. And at some point, you were contacted by Michelle McNamara, who was a crime writer, who had a widely read blog called "The True Crime Diary." A lot of people may recognize her name. She was married to Patton Oswalt, the actor and comedian, and she was quite a force. You want to tell us about your relationship with her?

HOLES: Yeah. You know, Michelle came into my life because of this case. She - initially, I treated her as just another writer that wanted to write an article, which, at the time - that's what she was doing. She was writing an article for Los Angeles Magazine. And I was very standoffish with her. But as her and I talked, we clicked. And eventually, as we continued to communicate leading up to the release of this article, that's when I divulged aspects of my investigation that were sensitive. And when her article came out, I was so nervous that she would burn me. But I saw that she didn't in the article. And at that point, I recognized I could trust her.

Eventually, she came up to Contra Costa County, and we spent a day where I'm driving her around to various crime scenes in my county as well as far up as Davis, Calif. And we're talking the entire time. She's recording the conversation. The conversation is about the cases, but it's also personal, you know, in terms of - you know, she's telling me about her - you know, her upbringing, her marriage to Patton, you know, the lifestyle that she's living down there in the Los Angeles area married to a celebrity. And she's getting to know me. And we really bonded.

And eventually, I would say we became investigative partners. I was on the task force, the law enforcement side, and she, at this point now, had been asked and tasked with writing a book. And she's the one that came up with the moniker Golden State Killer. You know, I had always known this offender as East Area Rapist up until the time Michelle renamed him. And I argued with her about, no, we don't need another name for this guy. But turns out she was right to the Golden State Killer - is a much more descriptive moniker than East Area Rapist or Original Night Stalker.

DAVIES: She tragically died in her sleep in 2016 from an accidental overdose of medications that she had been taking. She was working on this book and was under a lot of pressure to get it done. And she had this enormous, you know, trove of new evidence to go over. Tell us a bit about what insight you had into her work in those last months and about the last time you saw her.

HOLES: Yeah. Well, Michelle, though she had been tasked with writing the book, she really ended up trying to investigate the case. You know, she's - just became like one of the assigned investigators to where now she's investigating the case and not doing as much writing. And, you know, it's a huge case. There's a lot of pressure. You know, when you start looking at the - you know, you have 15,000 pages of case file information. Imagine how long it would take to read a novel that's 15,000 pages long. You know, so it's a lot of data to go through, and it's the emotional roller coaster ride - Michelle, just like I experienced, thinking, oh, I found a guy. He looks good. And then, ultimately, the DNA shows he's not the guy. And that's an emotional crash. And so she's experiencing that. Plus, she has the pressure of writing the book.

But ultimately, my last communication with Michelle was - you know, she was driving up. She had a young daughter who was in the Girl Scouts, and she was taking her daughter to some sort of camp, I think, just north of Santa Barbara. And Michelle emails me just saying, hey, you know, passing through Santa Barbara where, you know, the Golden State Killer had attacked three times, had killed four people. And she's passing the exits that he likely would have had to take in order to get out to commit these crimes. And she says, this is just such a surreal, you know, place to be with my daughter for Girl Scouts as I'm passing through where these horrific crimes occurred. And then, she just ended that email, you know, talk soon.

DAVIES: Six years ago, it still hurts.

HOLES: It does.

DAVIES: Yeah.

HOLES: You know, and then, I find out she - you know, she passed away, you know, a few days later. And she had - you know, one of the things that she had - what she was continuously doing was she was scanning all these documents. You know, she was putting them up in a file transfer service. And so she had let me know - I received an email, you know, from that file transfer service that there was something for Michelle waiting for me. And that - I received that email after I find out she had died. And I went and downloaded that file. And it's - you know, in some ways, you know, she was still helping me, so...

DAVIES: When she died, you know, the - I'll just wrap up this chapter by noting that when she died, the - her manuscript was substantially written, and her investigative partners worked with her publishers to get the book out. It's called "I'll Be Gone In The Dark." It was a huge bestseller, and it's also the title of a seven-part documentary series that you can still see on HBO, which our guest, Paul Holes, appears in. And it's also pretty gripping.

We're speaking with Paul Holes. He's a retired cold case investigator who still assists families and law enforcement as a private citizen. His new memoir is "Unmasked: My Life Solving America's Cold Cases." We'll be back after this break. This is FRESH AIR.

(SOUNDBITE OF KYLE EASTWOOD'S "SAMBA DE PARIS")

DAVIES: This is FRESH AIR. And we're speaking with Paul Holes. He spent more than two decades as a criminal investigator in California. He played a critical role in the identification and arrest of the so-called Golden State killer, who was responsible for at least 13 murders and 50 rapes in the 1970s and '80s.

So in 2017, you finally pursue a new approach that would crack this case and identify the killer. It involves DNA. It's a little complicated, but tell us what happened.

HOLES: You know, this technique really is what genealogists were using to help, you know, adoptees find biological parents. And it's a matter of taking, you know, your unknown DNA - our Golden State Killer DNA - searching the various genealogy DNA databases we're permitted to search, getting a list of relatives that share DNA with the Golden State Killer, and now just doing straight genealogy, relying on public records, in order to build family trees back to identify a common ancestor, somebody that the Golden State Killer would be a descendant of, and then building that family tree down into the current time and getting a list of names of people who all have a California connection, are the right age. And we just start investigating these individuals to try to determine, are they - do they circumstantially add up to being somebody we need to get a direct DNA sample from to compare to the DNA that we have from the crime scenes of the Golden State Killer?

DAVIES: Right. And you get a sense - if you actually see the family tree that you established, I mean, I think the common ancestor was back in the mid-19th century. So there's a lot of people. But you get down to people that are living today, people that are the right age, gender, etc. And you settle on this guy, Joe DeAngelo. What happened then?

HOLES: Well, you know, at this point, this is where I'm just now doing what I typically do in terms of vetting this DeAngelo as a suspect, you know? Who is this guy? Where was he located at in terms of his residence? Where is he purchasing firearms? And eventually, there's an article, a newspaper article found where he had been fired from Auburn PD for shoplifting dog repellent and a hammer. And he had been fired by this chief of Auburn, this Nick Willick. So I end up talking to Nick. And Nick, during that conversation, he doesn't know I'm looking at the east area rapist/Golden State Killer case.

He talks about when DeAngelo was on admin leave during the termination process, Nick's at home asleep in his bed. And his daughter comes into his room and says, Dad, there's a man standing outside my bedroom window shining a flashlight into it. And Nick says, Paul, I knew that was DeAngelo. I jumped up. I ran outside. I saw shoe impressions all around the perimeter of the back of my house. But I knew that was Joe. And that's when the hairs on the back of my neck stood up because I go, that's exactly what the Golden State Killer was doing. And it was really - that was really the turning point, where I'm going, OK, this Joseph DeAngelo, in addition to other aspects about him, that right there is where we need to get this guy's DNA and see if he is the Golden State Killer.

DAVIES: Right. He's 72 years old, living, I guess, married in a middle-class community in the Sacramento County. And eventually, you know, you get a match. People manage to grab some, I guess, a tissue from his trash and get a solid confirmation that it's him. A crew goes out, arrests him without incident. And you - although, at this point, by the time the arrest happened, you were no longer in government service, right? You had retired?

HOLES: I had retired. In fact, when he was under surveillance, I was out in Colorado with my wife, shopping for a house. And then I'm getting updates about the surveillance. And then, eventually, I get an update about an initial DNA sample, which was a mixed sample from his car door handle when he went to a Hobby Lobby. But at that moment, it was like, I know that's the Golden State Killer. And so when I got back to California, I end up going up and being embedded within Sacramento homicide and myself and a Sacramento homicide sergeant, Ken Clark, we lock ourselves in Ken's office and write the arrest warrant. And then I assist on the search warrant - just waiting for that second sample that you talked about, the piece of tissue, to get results back. And once that came back, then Ken was able to get the judge to sign it. And DeAngelo was arrested.

DAVIES: Right. And even though you had actually retired from county government in Contra Costa County, you were intimately involved enough with this case that you were actually able to observe him in the interview room. You were going to, hopefully, interview him. Tell us what happened.

HOLES: Yeah. You know, in fact, Ken and I had talked about a strategy in that Ken was going to go in initially, talk to him about the Sacramento cases. And then Ken and I were going to interview DeAngelo regarding the other Northern California cases that I had a high level of familiarity with before allowing the Southern California homicide investigators to go in. But once Ken goes in for his initial interview on the Sacramento cases, it was obvious that DeAngelo wasn't going to talk. He literally sat in the interview room and stared at the other wall, not even paying attention to Ken, not responding to his questions. And then, eventually, as that progressed, we recognized that talking to him about other sexual assaults in Northern California was not going to be a good experience for us. And we needed to let Southern California homicide investigators at least have a crack at him before he decided to invoke his rights for an attorney.

DAVIES: You know, it's interesting that you spent so much time, you know, going to every crime scene, visualizing what the offender saw, trying to understand his motivations and methods. And in the end, it was just this - the internet and DNA that really gave law enforcement the tools to identify him. Is he at all like what you had pictured?

HOLES: Yes and no, you know? As I investigated the case, you know, I really came to the conclusion that our offender is Sacramento based, probably still living in the Sacramento area, which DeAngelo was. And I also concluded that I am dealing with a sophisticated and intelligent offender. Turns out the offender, the Golden State Killer, was a former cop. He understood law enforcement tactics. He had been trained as an investigator for burglaries. So he had skill sets that were up and beyond the average person in order to be able to develop tactics and get away with these crimes.

DAVIES: Do you - I mean, what about the motivation, a guy who starts with burglaries then starts with rapes and then long terrorizing rapes of couples and then graduating to murders? I mean, do you have any kind of theory as to sort of why he progressed in that way, what need in him it fed?

HOLES: Well, you know, it's really theories because he's never talked. He's never told us, you know, exactly why he was doing these crimes. But he is the textbook example of the evolution of a serial killer. Different killers evolve different ways. But with DeAngelo, he started out as a peeping Tom, standing outside, looking in windows. He was committing burglaries. Then he starts committing fetish burglaries when nobody's home. After that, he progresses. He evolves into a serial rapist. He's now breaking into houses and attacking women and then ultimately couples.

When he loses his law enforcement job - and you have to remember, he went to school. He got his criminal justice degree. He worked as a Roseville PD intern. He gets hired down in Exeter PD down in Southern Cal - or middle California, Central California. He loses the thing that gave him that power and authority. What does he do? He goes down to Southern California and he starts killing. So now the loss of that power and authority as a law enforcement officer basically pushed him over the brink from being a serial rapist to a serial killer.

DAVIES: You've left government work now, but you've been busy. And one of the things you've been involved with is the kind of the true crime world. This is something that's really exploded in recent years. And, you know, I wonder, I mean, one of the things you write about in the book is sort of - is your empathy for the victims of crime and fury at criminals responsible for their suffering. How do you feel about people using this as entertainment?

HOLES: Well, I think this is where, you know, this is part of the message that I'm putting out there, because I very much am in the true crime genre. But I come out of real crime. And I emphasize to, you know, people like when I'm at the true crime conventions such as CrimeCon is that it is fine to learn about these cases, to learn about these offenders. You don't glorify the offender. But you have to realize that real people were affected. And some of these people are in this room if we're at a conference. And that is a fundamental message that I am trying to continue to press, is that, you know, of course, you know, we say it's entertainment. But within the true crime genre, we need to make sure that there is that ethical responsibility of understanding that this is real life. And it's OK to watch these shows. It's OK to listen to the podcast. But continue to understand that people's lives have been affected.

DAVIES: Paul Holes, thanks so much for speaking with us.

HOLES: No, thank you very much for having me.

DAVIES: Paul Holes is a retired cold case investigator who still assists families and law enforcement as a private citizen. In September, he'll be co-hosting a new podcast with Kate Winkler Dawson titled "Buried Bones." His new book is "Unmasked: My Life Solving America's Cold Cases." Coming up, Maureen Corrigan reviews Mohsin Hamid's new novel, "The Last White Man," in which white people mysteriously start to turn brown. This is FRESH AIR.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.