The evolution of using DNA testing to solve crimes

CHICAGO - It’s been nearly 30 years since DNA testing linked OJ Simpson to the murders of Nicole Brown Simpson and Ron Goldman. Since then, the process has gone through some major changes.

In a Fox 32 special report, Tia Ewing looks at how investigators can now do a lot more with a lot less.

Simpson’s 1994 murder trial is well known for a lot of reasons. One of them is the more than 108 exhibits of DNA evidence that were introduced, which included more than 60 drops of blood.

"When forensic DNA first started, we needed a quarter size stain of blood - pretty big," said Wendy Gruhl, who lectures on forensic biology at Loyola University. "Now we are looking at a couple millimeters or may be like an eighth of a centimeter for blood."

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Forensic biologists like Gruhl no longer need to depend on big samples of blood or other body fluids to get a DNA profile.

"You can collect samples from a shirt that you wore because you transferred DNA from your skin cells on to the collar of that shirt for example. Or on the screwdriver that was left at a crime scene," Gruhl said.

That’s because every time you touch something, like a door knob, your computer, or a phone, you leave behind skin cells, or Touch DNA.

Some of us leave more than others.

The human body sheds roughly 400,000 skin cells each day. Gruhl says investigators need only a small fraction of that to get a DNA profile.  

"The sensitivity is roughly on the order of 150 cells. The human body has literally trillions of cells. Not thousands, not millions, not billions. Trillions of cells. So the idea you could get a profile off 150 is pretty incredible," Gruhl said.

"I would say sensitivity greatly increased probably about 2007, 2008," said Brenda Danosky, biology program manager for the Illinois State Police.

"We don’t just do DNA on sexual assaults or homicides. We actually process property crimes. We process crimes against people. It could be a battery case," Danosky said.

Illinois State Police say Touch DNA they recovered from the weapon in an expressway shooting on I-290 back in March 2020 was used to convict the gunman.

There are some pitfalls to using this type of DNA evidence.

"The famous case that people talk about is this case out of California where there was this homeless man, and his DNA came back under the fingernails of a murder victim," said Lauren Myerscough-Mueller, an attorney with the Exoneration Project.

She has worked on numerous cases involving different types of DNA evidence and knows about the 2012 case against Lukis Anderson.

"He was arrested. He was charged, everything like that. He was very lucky that he had a very good lawyer who believed him when he said ‘I have an alibi. I could not have done this. You need to look into this,’" Myerscough-Mueller said.

Anderson’s public defender did some digging and confirmed paramedics had taken him to a California hospital the day a Silicon Valley investor was murdered.

"It happened that those same paramedics responded to the murder victim’s house and used the same pulse ox on the victim and transferred the DNA through the pulse ox. That’s how it got under his fingernails," Myerscough-Mueller said.

The charges were eventually dropped against Anderson.

"The danger is he was lucky he had an alibi he could prove he was somewhere else. Most people can’t prove they were somewhere else," Myerscough-Mueller said.

Myerscough-Mueller says it’s very possible other people are being wrongly convicted using Touch DNA because it was just transferred from something else and they are not able to prove their alibi.

"I think there are some prosecutor’s offices now who are more careful about bringing charges (based on Touch DNA) and the evidence required to do that. So my hope is that even if they have evidence from Touch DNA, they have additional evidence," she said.

One last interesting note, one expert we talked to says even if an offender wears gloves, they still shed DNA from other parts of their body, like their hair or their face.

The amount of DNA testing investigators need for all types of evidence has grown so much in the last several years that the Illinois State Police are in the process of opening a new crime lab that would be a first for them.

It would only do DNA testing.