The Game-Changing Role of DNA in Sexual Assault Cases

DNA evidence has become a routine part of prosecuting sexual assault cases. Research shows that 72% of jurors expect to see DNA evidence in a sexual assault trial, and juries are 33 times more likely to convict when DNA is presented[1][2]. This reliance on genetic evidence has made DNA a game-changer in achieving justice for victims of sexual violence.

But DNA’s role can be a double-edged sword. While it often strengthens the prosecution’s case, it can also exonerate the accused when properly analyzed. And controversies exist around how rape kits are tested and how DNA databases are used by law enforcement.

The Power of DNA to Secure Convictions

When DNA obtained from a rape kit matches the defendant, it can often seal a guilty verdict. Jurors find DNA matches to be definitive proof–much more so than eyewitness testimony or circumstantial evidence. As one prosecutor put it, “Jurors have come to expect [DNA], and they give it tremendous weight.”

DNA also helps overcome two common defenses in acquaintance rape cases:

• That the victim consented to sex.
• That no sex occurred at all.

Matching semen, saliva, or blood to the defendant contradicts both claims. And since rapists tend to be serial criminals, a DNA match can establish a pattern of behavior[2].

Preventing Future Rapes

Even when current prosecution isn’t feasible, DNA helps take serial rapists off the street. When victims agree to testing, it adds the perpetrator’s profile to law enforcement databases–enabling links to other crimes[2].

This DNA dragnet has helped solve many “cold cases”–sometimes decades after the assault occurred. For example, in 2018, genetic genealogy helped identify a serial rapist and murderer known as the “Golden State Killer,” more than 30 years after his crime spree[3].

Challenges Around DNA Evidence

Despite its power to convict the guilty, DNA evidence has limitations and controversies:

• The backlog problem: Hundreds of thousands of rape kits sit untested due to underfunded police labs. Automating parts of the analysis process could help[3].
• Inconclusive results: In many cases, no usable DNA is recovered, or test results are ambiguous. Advanced forensic techniques like phenotyping may provide more answers[4].
• Misuse of databases: Some oppose law enforcement searching DNA databases for partial matches. These “familial searches” can implicate innocent relatives[4].
• Privacy concerns: Collecting DNA from victims has raised privacy issues. In one case, police used a victim’s DNA to link her to an unrelated crime[5].

The Impact on Victims

The process of collecting DNA evidence can re-traumatize sexual assault survivors. But many agree to invasive exams because DNA often means justice. As one victim put it:

“I suffered through the investigations and the rape kit exam because I wanted the police to catch him before he hurt someone else.”[2]

When DNA goes untested, it sends a message that sexual violence isn’t a priority. Testing backlogs have left many victims feeling betrayed by the justice system[6].

Looking Ahead

DNA technology will continue advancing, providing police and prosecutors more tools. But challenges remain around funding, privacy, and earning victims’ trust. As one advocate noted:

“We should encourage survivors to come forward–not collect evidence to use against them.”[5]

In the end, the human impact should stay at the forefront. DNA evidence is meaningless unless justice systems treat victims with the care, respect, and urgency they deserve.

References

[1] Shelton, Donald E., Kim, Young S., and Barak, Gregg. “A Study of Juror Expectations and Demands Concerning Scientific Evidence: Does the ‘CSI Effect’ Exist?” Vanderbilt Journal of Entertainment and Technology Law 9 (2006): 331-368.

[2] “The Importance of DNA in Sexual Assault Cases.” RAINN, 21 Sept. 2023, https://www.rainn.org/articles/importance-dna-sexual-assault-cases.

[3] “Automation of Sexual Assault DNA Processing Increases Efficiency.” National Institute of Justice, 6 Sept. 2023, https://nij.ojp.gov/topics/articles/automation-sexual-assault-dna-processing-increases-efficiency.

[4] Murphy, Heather. “A Rape Survivor Gave Police Her DNA. They Linked Her to Another Crime.” Wired, Conde Nast, 24 Feb. 2022, https://www.wired.com/story/a-rape-survivor-gave-police-her-dna-they-linked-her-to-another-crime/.

[5] “‘Game Changing Technology’ Meant to Decrease Crime through DNA Testing, Chester County DA Says.” Daily Local News, Daily Local News, 31 July 2023, https://www.dailylocal.com/2023/07/31/game-changing-technology-meant-to-decrease-crime-through-dna-testing-da-says/.

[6] Lovell, Rachel, et al. “The Rape Kit Backlog: Failures of Justice and Well-Being.” Trauma, Violence, & Abuse, vol. 20, no. 3, 2019, pp. 313–325., https://doi.org/10.1177/1524838018767933.