Fingerprint database leads to killers

A car forced another to pull over alongside a road in St. Lucie County, Florida. A family of four occupied the other car - a mother, a father and two children, ages four and five. It was 2006.

The occupants of the first car shot and killed all four family members, and fled in the family’s car. Passersby discovered the bodies, but the suspects were long gone.

Police had a quadruple homicide on their hands.

The shooting happened along a toll road. Detectives went to the tollbooth and collected the video. They focused on the vehicles that entered at the same time or right before and after the victim's vehicle had entered the tollbooth.

Using these videos, investigators located the point where the victim's and suspect’s vehicles had exited the toll plaza. They collected the toll tickets.

Back at the St. Lucie County Sheriff’s Department, crime scene investigators processed the tickets with chemicals to make any fingerprints on them visible. Investigators entered those fingerprints into a SPEX Forensics automated fingerprint identification system (AFIS). The investigators compared the fingerprints they found with fingerprints already in their database. They also had access to a state police database.

Investigators found a match.

As it turned out, the suspects were drug cartel members, and the adult victims were dealing drugs. The murder involved a territory dispute,  and the case became part of a larger drug cartel operation that reached as far as Mexico. Prosecutors eventually pursued the case in federal court.

St. Lucie’s SPEX Forensics AFIS has more than 250,000 fingerprints in its database. The proprietary algorithms contained in the SPEX Forensics AFIS compares latent prints to those in the database. They can enter latent prints found at a crime scene into the system. AFIS will do comparisons to the known prints in the database.

The St. Lucie County Sheriff’s Department covers the county of 300,000 residents. The county is located north of West Palm Beach, between Miami and Daytona Beach.

Donna Carmichael is the crime scene supervisor and a 26-year veteran of the department. Investigators call her team to a scene of major crimes, and the team first documents the exterior while waiting for a judge to issue a search warrant.

“We will scan the scenes with the 360 degree scanners, take measurements and collect any evidence that's located outside of the search warrant area,” she said.

Once investigators receive the search warrant, they will video, photograph and diagram the scene. They use latent blood detection tools like Bluestar® or luminol to detect trace amounts of blood at crime scenes.

St. Lucie uses SPEX Forensics’ Mini-CrimeScope 400 and HandScope LED forensic light sources. Investigators use these to identify substances that might be evidence of a crime but invisible to the human eye. That includes fingerprints, body fluids, human skin damage, bone fragments, drugs, hair, fibers, and even shoe prints. The light sources operate at various wavelengths that are characteristic of the substances they are searching for.

“We use the HandScope to look for evidence or the areas that we've processed with the chemicals to see if we have any trace evidence at the crime scene,” she said.

Body fluids like semen, saliva, and vaginal fluids are naturally fluorescent, and the use of a light source offers a unique method for locating them.

Carmichael’s team uses the compact HandScope LED at crime scenes because of its size, convenience and light source capability. Investigators mainly use the larger Mini-CrimeScope 400 back at the lab to examine evidence, although it is also portable and travels to crime scenes on occasion.

The case of a sexual assault victim requires special treatment. Although it’s important to collect evidence of body fluids as soon as possible, investigators must take the victim’s emotional state into account.

“The the CrimeScope, bringing it out, due to its size can intimidate a victim, where the HandScope is much smaller and friendlier.”

The AFIS, which Carmichael called their friend, is also critical in solving crimes.

“We have a lot of burglaries and robberies where we don’t have a clue of who the suspect is,” she said. “We have many gang members in our area. Being able to put the prints into the database allows us to provide the detectives with the leads so that they can then investigate the case further and solve the cases.”

Carmichael has learned to deal with events like the quadruple homicide case where kids are involved.

“You're getting justice for the kids, because they're innocent victims. They can't help what their parents were doing.”

SPEX Forensics is a division of HORIBA Scientific.

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