SPRINGFIELD, Ill. – FOX 2 had an in-depth inside look at how the FBI gathers hidden evidence, from white-collar crimes to violent crimes.

The FBI Evidence Residence Response Team (ERT) comes into a room thinking, ‘just because we can’t see it, doesn’t mean it’s not there.’

ERT leader in Springfield, Illinois, Special Agent Michael Maguire, said wearing the proper protective gear helps to keep the investigator from contaminating evidence and to keep evidence from contaminating the investigator.

ALS (alternative light sources), commonly referred to as ‘black light’ can reveal hidden traces of bodily fluids and DNA. The ERT most often uses blue light. Orange/amber eyeglasses and camera lens cover filter out the blue light, which fluoresces traces of fluids people otherwise don’t see.

“Our naked eye can only see so much. This allows us to use science so we can see more,” Maguire said.

Liquid solutions are often sprayed onto areas under the light to detect blood, which does not have the same fluorescent quality as other fluids.

In the case of University of Illinois student Yingying Zhang, who was kidnapped, raped, and murdered in 2017, the ERT investigators used ALS to look for her blood in the suspect’s car. They instead found large swirl marks under the light.

“There were these broad sweeps that were consistent from personal experience from somebody cleaning,” Maguire said. “So, special attention had been paid by somebody cleaning that vehicle which was very valuable and ended up in the affidavit leading to the arrest of that subject.”

Her killer is now in prison for life.

Maguire also explained the process of dusting and lifting fingerprints: a delicate last resort; mess it up, and the print is lost forever.

“We photograph every step of the way because it’s the image of the print that’s valuable to us,” he said. “Every single thing that you find, ask yourself, ‘How could this tell the story that we’re trying to discover?’ You never know exactly when a physical piece of evidence might be critical to making a difference between a conviction or a dismissal. There’s not one thing, that makes a conviction, that makes victims whole, that gets the job done. It’s a whole bunch of pieces that come together.”

Such was the case of murdered security guard Ted Horn, of St. Libory, Illinois. Horn was killed in an August 2021 bank robbery in East St. Louis.

His killer was just sentenced to 50 years in prison, last month. It was the FBI-Springfield ERT that worked the case.