Forensic DNA Analysis

The plethora of CSI, Court TV, and other crime-related TV shows have given the public the impression that you can order up a DNA analysis and expect to receive results before the last commercial.


In the early 1950s scientists were racing to try and discover the structure of DNA. They were pretty sure it was genetic material but no one understood how it worked or how it could determine things like a person's eye or hair color, height, skin pigmentation, etc. Although dozens of the world's top scientists were studying DNA, none of them had any idea that fifty years later DNA would become a critical piece of evidence in criminal prosecution cases from thefts, rapes, and child abuse to abductions and even murders.

In the law enforcement world of 2007 DNA has become the cornerstone of a large number of criminal cases. DNA analysis is a very sensitive process that must be performed under strictly controlled and documented conditions if the results are to withstand the scrutiny of the defense in a trial. Unfortunately, the TV world has led the public, and in particular the potential members of juries, to assume that DNA results should be indisputable and immediately available. However, the time needed to obtain DNA analysis data is often much longer than investigators and prosecutors would like.

The Backlog Problem

If you lived in the television CSI world of Miami or Las Vegas, you could order DNA analysis on three samples taken from a victim, and cheek swabs from four potential suspects and then get your definitive results back before you could go out, eat a pizza for lunch, and return to your desk. Unfortunately, most of us have to deal in the real world where things cannot be accomplished in 60 minutes. Police forensic labs performing DNA analysis must work within the time constraints of the analytical technology. Extended sample preparation time, the need for repeat analysis for confirmation, and the laboratory backlog of samples is among the many reasons for the extended time period needed to obtain accurate DNA data.

While all these factors add to the timeline for analysis, probably the most important factor is laboratory backlog. Setting up a DNA laboratory and training technicians to run the required assays accurately is not an easy task. The cost of the necessary equipment is also quite high. This makes it difficult for smaller police department to set up their own lab and therefore must rely on state police crime labs or outside, commercial labs to perform their analysis. Backlogs at these labs have resulted in turnaround times of six months or more.

A laboratory backlog occurs when a lab simply has too many samples to analyze per day or week with the trained technicians and laboratory equipment available. If the backlog in a lab is approximately 100 samples and the rate of new samples received is a constant 100 per week, then at the end of a month the backlog is 400 samples; at the end of six months it is 2400 samples. This assumes an ideal situation where technician do not get sick or go on vacation, equipment does not break down and prosecutors do not add high profile samples (which must be analyzed right away) into the middle of the queue. If money were no object then labs could simply buy more instruments, train more technicians, work 24/7, and solve the backlog problem.

Solving the Backlog Problem—

If life was this simple then the solution above would work. However, things don't work that way. As DNA evidence has become more and more critical to convictions in all sorts of cases, the number of samples being submitted for analysis has grown exponentially. The number of independent commercial laboratories performing DNA analysis (150 labs) has grown over the last ten years as has the number of law enforcement laboratories (over 30 State labs). However, this growth has not been able to keep up with the growth in samples. Congress realized the need for added lab capacity and passed The DNA Analysis Backlog Elimination Act of 2000 which sought to identify the need and provide a means for federal funding (budget of $170 million over four years) in an attempt to meet this need.

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