Sneak Thieves and Cat Burglars BEWARE

DNA evidence puts law enforcement hot on the perpetrator's trail in high-volume serial crimes.


Stuver agrees investigators must broaden their thinking about DNA. "It's a hearty, robust molecule that sticks around for a long time," he says. A short time ago when Miami-Dade officials were investigating a homicide where an offender strangled a woman in a parking lot, the only clear evidence they had was a weathered piece of rope. Lab analysts found substantial amounts of DNA where the subject had grabbed the ends of the rope to pull it tight around the victim's neck. "We got so much DNA off of it," he recalls. "Our first thoughts were 'We'll give it a try, but we don't have great expectations.' But it proved us entirely wrong and it's just one example of many. You might think something that's been out in the weather or a rough surface may not be condusive to trapping DNA, but with DNA you can't make these blanket assumptions. You have to try and test as many things as you possibly can."

Navigating backlogs

Nearly every forensic lab in the county has a backlog for processing evidence. Adding DNA profiles for lesser crimes could bring these backlogged DNA processing centers to the brink of disaster. To navigate this storm, it's critical for agencies to limit the types and numbers of samples collected at property crimes, notes Gialamas.

"You don't want to go into a crime scene and collect 30 to 40 samples to process," he explains. "That would be a waste of time and effort. You need to hone in on where you get the best value."

Though Orange County employs more than 150 technical and support staff working in the crime lab, these individuals serve more than 100 local, state and federal agencies in the county. Yet, through good case management, where the lab limits samples from high-volume serial crimes to four, the department maintains its backlog rate at less than half the national average. Where most DNA laboratories experience a turnaround time of six to nine months, the Orange County lab offers an average 60-day turnaround time, with samples from major crimes usually being returned within 30 days.

Developing such a case management program, where crime lab officials review submitted evidence then determine which evidence provides the most probative value, helps reduce the number of samples processed, adds Stuver, who notes one of his job duties is to review submitted evidence for its probative significance. The case manager, when faced with a burglary scene, for instance, might find that blood where the subject appears to have cut himself will yield better results than DNA from a frequently accessed bureau drawer. Likewise, an item the offender left behind, such as a crowbar, has more probative value than a swab taken from a doorknob because it's possible to attribute the object's origin back to the offender. "A cigarette in a home where people don't smoke, clothing the subject left in the home or maybe a vessel the offender appeared to have drank from and left it on the counter — that's good evidence," he says.

What isn't great evidence, according to Stuver, is samples coming from surfaces touched by multiple individuals. Doorknobs, bureau drawers, etc., may yield DNA, but to be effective, the investigative agency must obtain elimination standards from every person who might have come in contact with the surface. "The DNA analyzed would be a composite of the various contributors' who would have come in contact with that surface," Stuver explains, noting a complex sample makes it hard for investigators to differentiate between the various contributors. "If it's a too well handled surface, you won't be able to get anywhere with it," Stuver emphasizes.

Another consideration must be whether to dust an area for fingerprints or collect DNA. The same sites being scanned for fingerprints are places DNA may be present, Lacks explains. But if investigators dust for fingerprints, it contaminates any DNA present. Thus, officials must decide between lifting a fingerprint and running it through AFIS versus collecting DNA and submitting it to CODIS. "When it comes to identification techniques, identifying individuals through fingerprints is hands down the best way to do it," Gialamas says. "When looking for DNA we may seek areas where fingerprints do not exist or where they are just smudges."

Some excellent sources of DNA arise where there's a partial print or a surface from which a quality fingerprint cannot be lifted. Take for instance a concrete wall; the grooves in the concrete make it difficult if not impossible to dust or lift a print from it. In this case, DNA is the better option. "It has to do with the surface the print is on, the quality of the print and then considering whether you will have a better chance of getting a hit through AFIS, which can be done back at the department, or through DNA, where you might have to wait two months for it to be processed," states Lacks.

Keep it clean

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