DNA: San Diego's tiniest snitch

How did your blood get inside the victim's body?

Patrick O'Donnell at DNA separator. “Certain questions are important."
  • Patrick O'Donnell at DNA separator. “Certain questions are important."
  • Image by Natalie Fiocre

DNA, the molecular organizer of life, is the storyteller of our time. In the hands of a modern criminalist, DNA can tell a tale of rape or hate or murder, or it can shrug its shoulders and say, "It wasn’t him.”

DNA chart. The test copies a section of the DNA sequence, which is unique to each individual.

DNA chart. The test copies a section of the DNA sequence, which is unique to each individual.

Patrick O’Donnell, who runs the DNA crime lab on the sixth floor of the San Diego Police Department’s 14th and Broadway station, looks like a cop, but in truth he’s a scientist. The morning I met him, a tech was going through the personal effects of a recent murder victim. The victim’s bloody gold pants lay on a counter, an elaborate western belt buckle (silver with gold star and spurs), attached to a leather belt, personalizing the gore. The tech worked with rubber gloves on the dead man’s belongings: California driver’s license, what looked like immigration papers, a wallet.

Steve Cordes even has that bemused smile Akroyd wears when he misunderstands something.

Steve Cordes even has that bemused smile Akroyd wears when he misunderstands something.

Everything was tinged with blood. He stopped his work to tell me about processing loads (about three murders per week) and the present rate of business (slow). Open shelves behind him held slots for nine bodies, each capable of storing a body-sized amount of evidence, but no bodies are brought here.

In the anteroom, large sheets of butcher paper covered linoleum counters (bloody clothing has to be dried or it molds). Cardboard boxes piled in stacks of two waited to be processed. The atmosphere, made clinical by the grey-blue cabinets, gave off the comforting vibe of reverence.

I was transfixed by the photo on the driver’s license; my mind raced to put clues of the man’s identity together. Hispanic male, cowboy buckle, immigration papers, CDL — maybe a ranch worker? A drunken party fight? A passion play? A stabbing or shooting? My wallet matched the dead cowboy’s, and I shuddered as I looked out the sixth-floor window at the storm-agitated clouds to the south. If I were murdered, I thought, my effects would come through this room.

Heading out of the evidence-processing suite, O’Donnell stopped to glance into the photo studio. Suspects are brought here, their pictures taken against a floor-to-ceiling screen. Overhead, high-powered lights on a tic-tac-toe grid bisect the ceiling. A technician worked with a high-resolution camera to photograph and magnify evidence.

Next up was the fingerprint recovery lab. More butcher paper lined the counters along with dishes of ultra-fine black powder, brushed onto objects for study. Though there wasn’t any evidence on the counters, O’Donnell warned me not to touch anything, so I placed my hands behind my back and leaned forward. My eyes were pulled to the ventilation hood with a 15-gallon fish tank inside. The tank’s sides were a bluish white, the aftermath of Super-Glue. Cyanoacrylate fumes expose certain types of fingerprints. Criminalists often release a giant packet of the glue inside a car to search for latent prints. The process destroys the car’s interior, but you figure, if a murderer or rapist’s prints are inside, it’s all part of the job.

Next to the tank, another drying hood held newspapers hung out like clothes in a closet. This technique, O’Donnell explained, allows fingerprints to be pulled off newsprint. Fingerprints retain an amino acid that can be tested for, allowing criminalists to reconstruct the print. Fingerprints lifted from newspapers — even Hollywood hasn’t thought of that yet.

Fingerprints are the primary way suspects are identified. As O’Donnell shows me the latent-fingerprint lab, Ed Palma, who works there, overhears and begins ribbing O’Donnell, suggesting that the next time someone wants to tour the DNA lab, he'll do it. Palma takes over, explaining how each fingerprint contains a reservoir of information, which is digitized by marking down the junctions between the ridges on each finger. This data is then fed into the computer that searches relevant databases and prints out a ranked list of possible matches, finger by finger. The fingerprints are then entered into another computer database that can search locally, statewide, en interstate. The amount of concordance is displayed as a number — in the thousands if it’s close, in the hundreds if it’s not so close.

Early on in the 12-year-old fingerprinting program. Palma says, suspects would give different aliases every time they were fingerprinted. The computer might then find matches for multiple individuals. Fingerprints matching “different” individuals usually means bogus names were given.

Palma says his system is better than what the FBI presently uses. Before the Feds will bet taxpayer bucks on new technology, they want to see how the industry sorts itself; they don’t want to buy the next Sony Betamax. (Japan was the first country to successfully implement this kind of fingerprint-matching technology.) Palma says the system can match latent fingerprints something like 15 percent of the time.

O’Donnell takes me past the polygraph department. He steps in, thinks better of it, and leads me to the handwriting lab. The analyst there, Randy Gibson, is working on a note left on a mirror, written in soap. Whether the murdered or the murderer wrote, “Joe is trying to kill me,” is not clear. Gibson claims that if he has enough evidence, identification is 100 percent accurate.

We move onto O’Donnell’s lab. He’s got a quick meeting at 10:00, so he hands me off to Steve Cordes, who prepares evidence for analysis. Cordes looks like a short Dan Akroyd; he even has that bemused smile Akroyd wears when he misunderstands something. Garbed in white lab coat, Cordes is working on the sexual assault of a five-year-old. The boy was grabbed off his bike at gunpoint, pulled into the suspect’s vehicle, and repeatedly violated. Cordes opens a manila envelope with the swabs collected from the victim. Each cotton swab is inside a glass tube, sealed off from contaminants. One is a little brown, one has some blood on it, the other two don’t show anything to the naked eye. Cordes also has a shopping bag containing some of the boy’s clothes. He’ll put them under different light spectrums to check for fluids.

The content of the rape kit seems puny compared to the horror of the crime. This case will get worked on quickly; they have a suspect and it may well go to trial. Working priorities for the department are court first, homicides second, sexual assaults third. Anything that isn’t tied to an arrest comes last. “We’d love to be able to work on ’em all,” Cordes says, “...if we had enough personnel or money.”

Serologists, those criminalists who match blood at the crime scene with blood from the suspect, used to be able to remove some of the doubt as to who did what to whom. Criminalists still do this kind of testing, but it’s not as powerful as DNA evidence. The most common DNA test, the PCR — polymerase chain reaction — makes the odds of a suspect randomly (wrongly) being accused 1 in 2000, leaving a 1999-out-of-2000 chance that the match between the suspect’s blood and the blood at the crime scene is accidental. That, Cordes points out, is devastating evidence.

A PCR test is essentially a copy machine. It takes a small piece of the suspect’s DNA (from a hair or some sperm or some blood cells) and copies a section of the DNA sequence, which is unique to each individual. Then it makes millions of identical copies. It’s not a perfect system, but it’s more precise than relying on blood types.

Cordes tells me about one case where the murderer used a kitchen knife without tangs (the prongs that, on a hunting knife, limit how far the blade can enter the wound). When the murderer’s hand slid up the blade as he stabbed, his blood was mixed with the victim’s (he bled all over the kitchen, too). In the past, bloodmixing would have made the evidence sketchy, now it all but ends the case before it’s started. “So, how did your blood get inside the victim’s body, eh?"

Proving that a certain person’s fluids weren’t left behind — known as “exclusions” — is much of what DNA-identity work is used for. A classic example is the Nordstrom case, where a woman claimed she was assaulted in a dressing room of the Fashion Valley store. The case was unraveled by DNA evidence. Cordes is proud of what the lab brought to bear in that case. After the DNA evidence contradicted the woman’s story, it was easy to ask her, as Cordes puts it, “Excuse me, but would you like to change your story?”

Cordes is the first screen; he identifies areas on the suspect where cells might be available for a PCR test. Semen (as long as it has sperm), saliva, blood, hair, skin — all offer the promise of DNA. And Cordes is looking for DNA.

Deoxyribonucleic acid (DNA) is a sequence of amino acids that organizes the proteins that make up each individual. Except in cases of identical twins, everybody’s DNA is different. The cells of our body — blood, bones, hair, sperm — each have DNA inside their walls, in effect marking everyone with an identifiable code.

Curious about his career decision, I asked Cordes if he ever thought he’d be doing this.

“No, I never thought I’d be looking at dirty panties for a living.”

The microbiology degree Cordes got from San Diego State opened doors, but mostly in hospital labs, and that got old fast. Without an M.A. or a Ph.D., research seemed out of the question. A forensic alcohol job beckoned, but then he became an evidence technician. If the police department requires his expertise, he still gets called to do “the less pleasant ones” — multiple homicides or a crime scene with lots of blood but no body.

“Sometimes you can tell what happened [when the body’s missing]. String a line back and calculate the blood-splatter angles. There’s a whole [science) called forensic bloodstain pattern interpretation. You go out and look at patterns, come back and use geometry, and then refute things the suspect says — claims about it being self-defense or such.

“People don’t realize that when they’re hitting somebody, blood transfers onto whatever they’re using — not the first time, but by the time you come back like this” — he mimes a baseball bat coming down on a skull — “you get castoff, and it gives you a nice line. You can see the arc where the person came back to do it a second time.”

Cordes recounts a case where the castoff marked lines on the ceiling, telling the whole nasty story. Baseball bats leave plenty of evidence — wood in the skull, for one.

Not everything under the criminalist’s purview is based on organic matter. Non-DNA fibers often reveal secrets to the scanning electron microscope. Car paint, usually left behind in hit-and-run crimes, can be narrowed down to make, year, and model. The microscope is the most expensive piece of technology in the lab, used primarily to detect gunpowder residue. Even more interesting is the ballistics lab, housing some of that cruise-missile, terrain-hugging technology that matches shell-casings spent from assorted firearms. Eighteen hundred guns reside in there, along with Rush Limbaugh on the radio.

The rape kit for the boy’s attack contained a penile shaft swab, a rectal swab, a swab from his throat, and one from the buccal area. By using a black light, investigators fluoresced a place on the child’s thigh that might have been touched by the perpetrator’s fluids. They took a swab of that, too.

Looking for semen is central to sex crimes. If Cordes finds some, he’ll fill out a DNA request and then one of three DNA testers takes over. Cordes has many ways to find the stuff; one method is using the Alternate Light Source, an adjustable illumination device. Wearing red goggles, he’ll look at the boy’s clothes at about 430 to 485 nanometers (bluish-purple light). The fluids he’s looking for will give off a yellowish-green florescence under those conditions. (Florescence is just a fancy term for using light — black light in this case — to make dried-up liquids shine.) He can then mark off the area on the clothing and use a chemical test.

Another method of identification is an amylase test. Amylase is an enzyme found in saliva. Saliva has cells, and cells are what DNA criminalists want.

“Just had a case like that — robbery suspects. They had bandanas on. In order to find [someplace on the bandana] that might be tested for DNA, we had to find the area where their saliva was. So we map it out on plates, you make a map of the amylase, and where the starch is missing it shows you where the amylase actually is, because it digests starch.”

Looking back at the rape kit, I wonder how the constant reminders of man’s inhumanity play out in the minds of these scientists. I asked Cordes how he stayed imaginative.

“You have to keep an open mind, because the absence of something can be indicative of what did or didn't take place. Anytime you have a transfer between two people, or between one person and an item, you expect to find traces of one on the other. If you’re getting a complete absence, then it might lend credence to the story that it didn’t happen. You’re looking for traces...you re looking for other debris that might be indicative of someone else.

“While you’re trying to be meticulous about what you re doing, at the same time you’re looking for something out of the ordinary— the lack of something you’d expect to find. And you annotate that in your notes so you can testify to the full questions.”

I imagine criminals must be getting hip to these methods of evidence-gathering. “Are we educating the criminals with this new knowledge?” I ask.

“We’re educating people who do sexual assault that they wear a condom,” Cordes answers, “and they don’t just throw it down, they take it with them.”

The used condom has all the evidence a criminalist needs to link the rapist to the assault. It can’t prove consent, but that’s another story.

“Once they’ve gone through the system once, they learn what not to leave at a crime scene. They become educated very rapidly.”

O’Donnell returns. He points out that perpetrators are in an intense emotional state when they commit crimes, often too involved to cover their tracks. They tend to leave their own genetic calling cards. “Fifty percent of our homicides involve narcotics,” he explains. “Either the person was using narcotics, buying narcotics, or was on narcotics. Maybe a former husband comes back, pissed off, stabs her, stabs her roommate, totally out of control....

“We hear what the scenario is...because in a lot of cases it leads you to areas you might not look for what happened,” adds Cordes. “If the person’s been sodomized you’re going to spend more time looking at the back of their clothes.

“You’ll hear a story — and I think everybody is guilty of this — and you kinda get an idea of how the thing is going, and (then] you get surprised...occasionally.”

“You need to know something about what went on," O’Donnell says. “Certain questions are important — to know where the victim was...to know whether she had sex in the last 48 hours.... At the same time, you don’t want to frame it. For example, in a lot of homicides we’re starting to do the analysis, and we’ll [DNA-identify] the evidence, then we’ll go back and type the references, and lo and behold we get this strange DNA type on the victim’s reference blood sample. Then we call up the detective and it turns out this guy was shot and was given ten units of blood at the hospital.

“Now we’re looking at a reference blood sample that was taken at the morgue after this guy died, after going through the emergency room and receiving 12 units. We’re looking at the donor’s DNA type. At that point, we need other blood samples.”

While discussing certain cases, O’Donnell and Cordes avoid specifics, letting words like “stuff” and “things” and “it” and “evidence" stand in for the gory details. (I notice the pronoun “he” is generic for perpetrator.) And the work they do is not just for the prosecution. O’Donnell says he searches for the truth of his science, not just to identify bad guys for the cops.

“In general, 20 percent of the tests run are exclusionary. We’re viewed as a prosecution tool because we work at the police department. But one in five DNA tests we run, we arrive in court and say, 'This person could not have contributed to the body fluid.’ ”

“Do defense attorneys come to you?" I ask. “Do they say, ‘I want this done’?”

“Either it’s driven by the detective down at homicide or sex crimes or an attorney over at the district attorney’s office,” says O’Donnell.

“The defense has a right to part of the sample,” says O’Donnell. “If I have a quarter-sized blood stain, and they push the issue, that blood stain will be split. We’ll get half to screen, and they’ll get the other half and go to these other labs and perform the test."

Cordes mentions another type of DNA testing, which virtually eliminates the possibility of a chance agreement. It’s called RFLP, which stands for restriction fragment length polymorphism. It doesn’t copy a little piece of the DNA, it uses all the DNA from the actual sample. (PCR tests a piece of the bar code, while RFLP tests the whole code.) Since a much bigger strand of DNA is used, the odds that the DNA randomly matches another person on the planet increases by a factor of 10,000. In other words, the odds that two different people will show a matching RFLP test are 1 in at least 20 million.

It takes a few months to get RFLP results back, while the PCR test is much quicker, maybe four or five days. Another downside to RFLP is that you need a good-sized glob of blood to do it, whereas a PCR test can be done with an infinitesimal amount of material.

Either way, O’Donnell feels strongly about the quantum leap DNA offers in accountability, demonstrated in gang-rape cases.

“I’ve handled a couple of (them), one in particular where three suspects were involved. Using traditional [blood typing], it would have been impossible |to go to trial]. You’ve got the victim’s secretions and potentially three others’ secretions all mixing together — and you’re gonna try to resolve whether there is Type A present? Hopeless.

“The suspects were arrested shortly after the incident, and they hadn’t showered, [so we took] penile swabs from all three of them. Most people [think] we’re going to get sperm. (But] we do the other thing — we look for her type on their swabs; we look at [her cells] first.

“What if you’re looking at number one in a gang rape?” O’Donnell asks me, pop-quizzing like a teacher. “You’re only gonna have one sperm on the penile swab. Number two and number three — what are they gonna have?”

“They’re gonna have the other guys,” I suggest. “Then you can sequence them.”

“That’s exactly what happened,” O’Donnell says. “[We] looked at two of the people, and they definitely had sperm types that were not consistent."

In this case, all three suspects pleaded guilty to attempted rape. There were, O’Donnell says, some “mitigating circumstances” because the woman was intoxicated. “But if you had this case five years ago, these guys would’ve walked, no question. Because there would have been no physical evidence to resort to."

PCR testing is adequate for most cases — it has to be; the more powerful RFLP requires much more DNA. “We’re hoping to purchase [updated PCR] technology over the next six months,” O’Donnell reports. When they do, the SDPD crime lab will be the first in the state to have such technology.

I conclude my tour of the crime lab by talking to an old veteran of the evidence game. Larry Turner’s been working as a criminalist for a long time; he was spending his last day working in the DNA crime lab when we met. Turner worked on the Cleophus Prince case, which shook this city. But the case that remains in his memory is the first crime scene he worked, a multiple murder that took place in Mississippi. “I remember it just like it was yesterday,” Turner says.

The killer was the mentally unstable half-son of a wealthy man. Unable to frighten his father into giving him money, the son took the father into a secluded wood and shot him in the head. Turner found the sisters. The older one, about 14, had been raped, then shot. The younger one was curled into a fetal position, eyes still open, hands covering her head. Turner remembers those eyes, fixed in death. “It was like she was saying, 'Why me? What did I do?’ ”

Turner doesn’t have to go out to crime scenes anymore. And every time he takes a shower, he remembers how Cleophus Prince sneaked into the unlocked homes of his female victims while they showered. Larry makes sure to lock his bathroom doors now, and the outside door as well.

Solving sexual assault cases — positively identifying potential suspects — is what drives DNA use. The San Diego Police Department’s DNA lab, in operation since 1992, is largely Patrick O’Donnell’s scientific creation. He’s glad to put his knowledge to practical use, though sometimes he thinks about moving into the private sector. But O’Donnell enjoys applying science rather than theorizing about it. And besides, as colleague Turner points out, once you start speculating about why a particular crime happened, once the “what ifs" start, you’re already deeply involved.

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