Triaging DNA Evidence at the Crime Scene
Written by Kristi Mayo   

DNA analysis technology moves closer to the crime scene each day, it seems. The latest step in that direction is the ParaDNA system that allows law enforcement to determine the quality and investigative value of human DNA in 75 minutes. The product was developed by LGC Forensics in the United Kingdom and is now distributed exclusively by Life Technologies Corporation.

 


The ParaDNA system screens evidence for the presence of DNA - while also indicating the quality of the DNA present and the gender of the donor.

This particular technology is not exactly Rapid DNA, stressed Dr. Jack Ballantyne, a researcher and associate director with the National Center for Forensic Science at the University of Central Florida. His department is currently performing an independent validation study on the ParaDNA system. “Rapid DNA techniques are much more costly,” he said, “and they provide a full DNA profile. That is not what this is doing. It’s a screen. It’s much cheaper. And it’s easier to use than some of these Rapid DNA systems.”

How it Works

The ParaDNA screening system offers law enforcement or forensic laboratories a way to triage crime scene evidence and determine how to prioritize the submission of samples for DNA analysis. Here’s a brief explanation how it works:

After rubbing the sample collector on the evidence (or sample swab) to be screened, the collector is snapped into a reaction plate. Up to four samples in four different reaction plates are inserted into the screening unit and locked in place. The person doing the testing can then walk away and leave the instrument and software to complete the process. After approximately 75 minutes, the ParaDNA software displays the results. The system produces a relative score (0 - 100%) that is indicative of the quality and quantity of template DNA in the sample. In addition, the system amplifies amelogenin and outputs the gender of the sample’s contributor.

By Ballantyne’s estimation, anyone could be fully trained on the instrument in less than one hour. “I would say it’s one of the simplest instruments I’ve ever had to use in my scientific career,” he said. “It’s sophisticated instrumentation when you think about what’s going on (behind the scenes), but it’s actually very simple to use.”

Two Levels of Intelligence

The people behind ParaDNA believe this information will enable law enforcement agencies to be more selective when deciding what samples to submit for analysis to their labs. For example, if an agency has a policy that limits submissions from burglaries to five biological samples per case, a crime scene investigator could screen the samples and select the five with the highest DNA score. Or, in the case of an assault on a female victim where the suspect is most certainly male, investigators could screen the samples and eliminate any that came from a female contributor.

“It’s a screening test that enables the crime scene investigator or their lab person—whomever it may be—to make a very fast decision about which samples will be the ones tested for further DNA analysis,” explained Ballantyne. “It’s a quantitative approach to screening.”

But identifying the most informative samples with the screening assay is just the first step. Nadia Altomare, who heads up the human identification business for Life Technologies, said a second assay will be released on the ParaDNA platform later in 2013 that will provide more intelligence for investigators. The new product will have “the ability to discriminate and provide information on some specific loci.”

Ballantyne, who has briefly tested the forthcoming ParaDNA intelligence system, said this could be very important to investigations—particularly on the local level. The intelligence system, he said, provides five of the 13 CODIS STR loci, with genotypes. He presented an imaginary scenario: “Say you go to a burglary and you have a profile, and that five-locus profile is not unique to any one person in the country… but only one in one million people would have it. Well, in a small town, that one in a million is good enough for intelligence purposes,” said Ballantyne. “You can at least proceed with the knowledge that there is a high probability that it will be that person. Then you would have to get proper tests later on. But at least it’s good information—to link cases, for example.”

Rapid DNA at the Crime Scene

The information provided by the ParaDNA screening system—and the additional intelligence promised by the next iteration due out later this year—occupy a space in the marketplace that is very close to Rapid DNA… but not quite. That technology, observed Ballantyne, is likely several years away from being truly “ready for primetime.” That’s because developers looking to take Rapid DNA analysis to crime scenes want to produce profiles of high enough quality to be submitted to CODIS and in court.

“The systems that are being developed now, however, do not have these precise quantitation methods,” said Ballantyne. “Because of that technicality of how much DNA is being added, I think that’s going to set them back a little in terms of its use in crime scenes.”

The use of Rapid DNA for applications such as reference samples or identity verification at border crossings, on the other hand, may be deployable within a year, predicted Ballantyne.

“Placing ParaDNA in the hands of investigators will enable a quick and simple, on-the-spot presumptive DNA screen to complement today’s submissions policies and augment today’s lab practices—saving time and cost in the investigative process,” said Altomare. “We will continue to bring innovative products into the hands of law enforcement, crime laboratories, and military, developing useful centralized and decentralized solutions that make a difference in efficiently solving crime worldwide.”

About the Author

Kristi Mayo is the editor of Evidence Technology Magazine.

 
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