In DNA fingerprinting, the mystery may be in the sample
New QIAGEN solutions help forensic labs solve crimes while saving time and money
In solving a crime, one piece of evidence can provide the critical link. A trace of tissue, blood or saliva may hold the DNA that makes a definitive connection – from the victim or crime scene to the perpetrator. But establishing that biological proof is extremely demanding for investigators.
Evidence from the scene of a crime often comes in tiny amounts known as “trace.” Scientists in forensic laboratories use precise molecular technologies – but they work with samples that are far less than laboratory pure. The DNA may be contaminated, degraded or too scarce.
“The toughest job is analyzing ‘touch evidence,’ such as skin cells collected from a cord ripped out of a wall. You swab the end of the cord to try to find the DNA from the person who held it. You’re not going to get a lot of DNA to start with, so you really need every step of the analysis to work, and you need it to work the first time,” says Special Agent Charles Hardy, forensic scientist supervisor for the Tennessee Bureau of Investigation.
From breakthroughs to overloaded labs
DNA fingerprinting was developed in the 1980s, based on the insight that each individual has a unique genetic profile that conclusively establishes identity (except for identical twins, whose DNA matches each other). The breakthrough technologies for matching a suspect’s DNA against evidence from crime scenes, including running samples against databases of past crimes and offenders, have spread throughout law enforcement and the justice system.
But proving guilt – or innocence – is not as easy as a one-hour episode of an evening TV show. The processing of biological samples and sequencing of DNA are time-consuming and costly.
Crime labs in the United States struggle to keep up with the demands. With around 400 accredited forensic crime laboratories analyzing more than 4 million casework samples for investigations and reference profiles for databases each year, the United States is by far the largest market for human identification and forensics.
In casework and databasing, backlogs are the rule rather than the exception. Analysis of crime scene evidence often takes months and can delay investigations. Rape kits, the biological evidence collected from sexual assault victims, stirred national controversy in 2014 and 2015 because hundreds of thousands of the kits are stuck in backlogs, untested. Crime labs also perennially run behind on routine DNA profiling to enter into investigative databases.
Yet the role of DNA fingerprinting continues to grow. The FBI is expanding the required number of DNA markers (locations within the genetic material called short tandem repeats, or STRs) to be stored in its CODIS (Combined DNA Index System) database, from 13 markers now to 20 by 2017. The larger number of markers will enable more precise matches with DNA from investigations.
Similar technological advances to maximize the investigative power of DNA fingerprinting – along with the challenges of an expanding caseload – are occurring all over the world.
“The world of forensic DNA analysis has grown smaller and bigger at the same time. We can gain more information from a much smaller amount of DNA, while at the same time demanding more and more information from each examination.”
Special Agent Charles Hard, Forensic Scientist Supervisor for the Tennessee Bureau of Investigation
New solutions for forensic frustration
Now QIAGEN is offering forensic laboratories a new line of DNA fingerprinting consumables – with novel enhancements to streamline profiling for human identification. Following the successful commercialization of STR kits in all other regions of the world, the company recently launched two of its new Investigator® STR assay kits in the United States.
The STR kits incorporate QIAGEN’s innovative Quality Sensor to evaluate the quality of DNA in each sample, a unique technology that enables labs to decide which evidence may provide valuable results (and which samples will not). The Quality Sensor eliminates guesswork and trial-and-error troubleshooting with multiple runs of samples in search of usable DNA.
“Closing cases in forensic investigations demands quick decisions and reliable, understandable results. Often, the quality of DNA in trace amounts of evidence is the biggest challenge. Building on QIAGEN’s position as the clear leader in innovative sample technologies, we have integrated the Quality Sensor into these kits to give laboratories the insights they need to make confident decisions about the quality of each sample from a crime scene or investigation,” said Dr. Thomas Schnibbe, Senior Director and Head of QIAGEN’s global forensics business.
The new human identification kits provide an integrated solution to simultaneously analyze multiple genomic markers for DNA matching. The Investigator STR kits comply with the U.S. requirements for expanded marker sets by 2017, as well as meeting European and Interpol standards for forensic analysis.
The Investigator STR products QIAGEN is launching in the United States, approved for use with the CODIS network, include a multiplex assay kit for casework samples and one for reference samples. (To see details, visit https://www.qiagen.com/de/products/human-identity-and-forensics/)
These kits streamline genetic profiling and save resources for laboratories by focusing the work on usable DNA samples and avoiding time-consuming reruns of evidence. With the introduction, QIAGEN becomes the first new entrant in more than 20 years in the U.S. market for STR kits.
Importance of measuring sample quality
As with most genomic analysis, forensic DNA profiling depends – first of all – on the samples. At crime scenes, police or forensic teams may collect blood or suspected semen, cigarette butts or bits of food, or swabs from something possibly used in commission of the crime.
“The world of forensic DNA analysis has grown smaller and bigger at the same time,” says Agent Hardy. “We can gain more information from a much smaller amount of DNA, while at the same time demanding more and more information from each examination.”
Every forensic lab, he says, faces challenges in applying ever-greater technological capabilities to ever-smaller bits of evidence.
“When you’re dealing with touch evidence, you really can’t see it. So when you think you might have something you swab it all, take that swab and run it through, because you’re trying to get as much DNA as you possibly can,” Agent Hardy says. If the lab has problems in analysis, the cause could be degradation of the DNA, a chemical inhibiting the reaction, a problem with the laboratory reagents – or there may be no DNA in the sample in the first place.
“You’re not going to get a lot to start with, so being able to assess the quality of the sample you are analyzing is key,” says Agent Hardy. “If you’re facing thousands of DNA analysis requests a year, you don’t really have time to fool around trying to figure our why your amplification didn’t work, or why you’re not getting a profile. And you can waste a lot of material, sometimes the whole sample, trying to figure out why your sample dropped off so bad on the analysis.”
The Investigator Quality Sensor integrates assessment of the quality of DNA into the same test that detects markers for identification.
“The Quality Sensor is a powerful troubleshooting tool to save precious time and lab resources,” says Agent Hardy. “When you look at that DNA profile with the Quality Sensor, and you’ve got the two sensors showing, you can have confidence in the results. Be it a good profile, or a bad profile, at least you know what is going on. It helps you move forward with peace of mind.”