CSI Sully District Station

CSI Sully District Station

Detective discusses fingerprint forensics.

Forensics can be a fascinating field, and members of the Sully District Police Station’s Citizens Advisory Committee recently got a glimpse into the world of fingerprint analysis from Det. Derek Hardy.

A 20-year police officer, he’s spent 14 years in forensics and is a member of the station’s Crime Scene Section.

“Prior to 2008, we couldn’t do one-tenth of what we can do now, because of the technology,” he said. “And the public’s financial support of the new crime lab [at the public-safety building on West Ox Road] helps us put away rapists and murderers.”

Discussing these forensic-technology advances, Hardy said fingerprint methodology consists of analysis, comparison, evaluation and verification.

“We do verification because I have to verify the validity of my results,” he said. “Fingerprints are the best evidence — better than DNA — because DNA will say the suspect can’t be eliminated. But a suspect’s fingerprint is only his. Even identical twins have different fingerprints because they have different ridge patterns.”

Hardy goes through several steps in doing his analysis. He sees if the fingerprint was deposited on a porous or nonporous substance. He also determines the composition of the fingerprint residue.

“Are there oils, dirt, grease, grime or sweat?” he asked. “And are there any foreign materials in it — blood, ink, paint, etc.? The most common is a mix of these substances.”

Then Hardy decides whether to use a chemical or dry process to develop the fingerprint impression to make it glow in the dark and be better visible. “We’re looking at the evidence before it’s processed,” he said. “And sometimes, we have to use more than one process to bring out a fingerprint.”

Crime-scene detectives also have to be able to take photographs to uncover fingerprints, said Hardy. “A coherent tracer is a green, forensic laser system,” he said. “It’s like a magic flashlight specifically for forensics, and we can see fingerprints, fibers, body fluids and narcotics residue with it.”

“The more fingerprints we can find, the more bad guys we can find,” he continued. “So it pays to have this technology. The fingerprints will also show the position of the sweat pores, which are also different on everyone.”

Hardy discussed the Reflected Ultraviolet Imaging System (RUVIS), as well. On objects, it helps police find fingerprints that, otherwise, they wouldn’t be able to see — even with the laser and chemicals.

“But RUVIS can degrade DMA, so I’d try to capture the fingerprint’s DNA first, before using RUVIS,” said Hardy. Currently, Fairfax County doesn’t have this system, but he hopes one day it will. In this county, he said, “We have to lead the charge and keep up with this technology.”

He also noted the huge advances in forensic photography, which police here do employ. “It’s HDR photography, which provides more detail on fingerprint photos,” said Hardy. “I take multiple photos of the same thing at different exposure settings to see the whole spectrum. I capture all the details of fingerprints and sweat pores put together.”

Proud of what this county offers, he said, “We continue to lead this region in forensic technology. We’re one of only nine police departments in the nation using HDR photography. We’re the only one in this region using a laser, and we’re hoping to get a RUVIS. We have new equipment and our new crime lab is about 12 times larger than what we used to have.”

Sully District Station Commander Ed O’Carroll said the work Hardy does at the crime-scene level and the work done by Officer Mike Roberts at the station to connect fingerprints to crimes and suspects is “one spoke of the wheel.”

“Det. Hardy is one detective of many who respond to major crimes — rapes, robberies and homicides,” said O’Carroll. “The uniformed officers respond first and then the detectives; we have four Sully detectives assigned to our Criminal Investigations Section. So it’s a layered approach when it comes to investigating. Even if we catch the bank robber with a bag of money, we’ll get a fingerprint or footprint because we’ve got to make that case in court.”