Forensic Dye Research

Aug 22, 2013

Forensic Dye
Credit University of Virginia School of Nursing

When a woman reports a rape, she is given a forensic evidence exam--known informally, as a rape kit. 

But the rape kits used by hospitals all over the country are using a technique that puts women with dark skin at a disadvantage.  


Kathryn Laughon, UVA Researcher
Credit University of Virginia School of Nursing

The first thing that happens when a woman goes to the University of Virginia hospital and reports a rape--she’s offered choices.  

"So when a victim comes in, we find out what the victim wants to do.  At a minimum, we’ll make sure that the victim is physically okay," says UVA nurse and researcher Kathryn Laughon.

The victim is offered medication to prevent STDs and pregnancy.  An advocate is called to offer support for her.  Then, if the victim is interested in pursuing criminal charges, the hospital performs a sexual assault forensic evidence exam, also known as a rape kit.

"And that is a physical exam looking for any kind of injury, not just injury that is medically useful, but small scrapes, and bruises.  We document using photography any evidence we see, we collect samples if there’s any debris attached to the body so that it can be preserved for later forensic evaluation."

Surprisingly, rape kits weren’t widely performed until the 80s, but thanks to shows like Law & Order, the procedure is pretty well known now.  One key part of the rape kit is a genital exam, which uses a special blue dye to highlight injuries.

"So we’ll look and see if we see any injuries, very often though, the kinds of injuries that might be important for a criminal case are not easy to see. And so we use this dye that lets you see structures in the cell. So I can put the dye on and wipe it off and anywhere there’s a break in the skin turns bright blue."

This part of the exam is huge in a court case.  While evidence of injury isn’t necessary, it can really help.  Laughon says that strong evidence from the blue dye is associated with twice the likelihood of achieving a guilty verdict in court.  But here’s the catch.

"If the skin is dark, there’s no contrast with the blue dye.  And so the blue dye does not in fact help with visualization on dark skin. We see fewer injuries in dark-skinned women than in light skinned women."

Nearly 1 in 5 American women have been sexually assaulted.  The rates of sexual assault per 1000 women are higher for women of color than they are for white women. And yet, this blue dye used in rape kits all over the country, barely shows up on dark skin.

"You know, I was just doing exams and when I had a dark-skinned woman, I used the dye and yet every time I did it, I would think, eh, this isn’t really helping me."

So Laughon decided to come up with something that could help.  She and two of her colleagues have been researching alternative dyes that will work equally well, regardless of skin tone.  One early front runner is a fluorescent dye.

"If anybody’s ever had a scratch on their cornea, when you go to the doctor what he or she does is put a fluorescent dye in your eye and look at that under a special light and if there’s a scratch there it will show up an orangey color."

Before a new dye can be settled on, it has to undergo exhaustive testing and research.  Just a few of the things that the team will be looking for?

"We need to make sure the dye does not interfere with DNA analysis. We need to make sure that it doesn’t hurt when it goes on. That it’s easy to put on and wipe off and take photographs of."

Laughon’s team has finished their preliminary research, but they’re waiting for the funding that’s necessary to start lab testing.  Laughon says that, while many women opt out, she firmly believes that every woman who chooses to go to court should be on equal footing.