Timothy O. McCalep

Rape kits and the potential limitations of DNA evidence, P.1

One of the issues readers may have heard about in the news at some point is the backlog of rape kit testing in many states across the country. Organizations like End The Backlog (www.endthebacklog.org), are dedicated to spreading awareness about the issue and prompting initiatives to address the backlog.

Different states have different approaches when it comes to addressing rape kit testing and backlogs. Georgia law requires annual auditing of untested rape kits, and all rape kits are eventually supposed to be tested. Georgia law does not require law enforcement agencies to track rape kits, so it isn’t clear how many are left untested, but the Atlanta Journal-Constitution reported in January that there were over 10,000 rape kits awaiting testing at the Georgia Bureau of Investigation. 

One thing for sexual assault defendants to keep in mind about rape kits is that while DNA evidence unquestionably has value in solving sexual assault cases and it will continue to play an important role in both sexual assault investigation and prosecution, there is still room for error. The reliability of rape kit evidence cannot necessarily be taken for granted in criminal cases.

For one thing, while the ability to extract DNA from human samples is greatly improved from where it was years ago, the way DNA is analyzed in some cases is questionable. This is especially true in cases involving human samples which contain mixtures of DNA, or cases where the sample is small or degraded. In these cases, reading the DNA can involve guesswork. In addition, testing standards vary, as does the level of training and quality control in place at testing facilities. 

While DNA contamination can be prevented with the use of proper collection techniques, DNA transfer from one person to another also needs to be considered, as does the strength of the DNA profile, which depends on various factors. Because of the fact that greater emphasis is now placed on less substantial evidence than in the past, probabilistic DNA testing and the consideration of exculpatory evidence is becoming increasingly important.

In our next post, we’ll continue looking at this topic, and the importance of working with experienced legal counsel to build a strong defense case against charges of sexual assault.


The Atlantic, The False Promise of DNA Testing, Matthew Shaer, June 2016.

End The Backlog, Georgia Backlog Snapshot, Accessed August 2, 2017. 

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