The St. Paul police crime lab — now dubbed the forensic services unit — had a show-and-tell of sorts Thursday at an open house designed to show off its new equipment and also help it shed its tainted image.

The crime lab came under fire last year after two public defenders challenged its scientific credibility in several drug cases. Subsequent audits found widespread failings in staff skills, poorly maintained testing instruments and illegible lab reports.

"We did an extensive, extensive review of what we had, where we had some challenges, what we were doing right, what we were doing wrong and where we needed to make some changes," said Mayor Chris Coleman, who toured the new unit Thursday with Police Chief Tom Smith.

The city invested $1 million to upgrade equipment and lab space and make improvements in the unit on the third floor of the Police Department's main offices. The new forensic services unit, which opened in June, also got a new civilian manager — Rosanna Caswell, a certified latent print examiner — to oversee the lab.

Police hope the unit will become accredited within the next two years, Smith said.

"This was a tough challenge, and I said a year ago we're going to unturn every stone, we're going to take a look at what we need to change, and we've done just that," the chief said.

Thursday's tour offered attorneys and city officials demonstrations of how the new equipment is used.

One of the most promising new technologies is a reflective imaging system called RUVIS that uses ultraviolet light to detect fingerprints.

In one homicide case, it was visualized a fingerprint on a cellphone that was dropped at a crime scene. Examiners ran the fingerprint through a database and were able to report an ID to officers within a few hours.

Unlike other methods at the lab's disposal, RUVIS didn't damage the phone and police could still retrieve data from it, Caswell said. "It is something that adds a lot of functionality to this latent print unit," she said.

The forensic services unit does general crime scene processing, fingerprint processing and comparison, and reconstructions of crash and crime scenes. The city pays for the state Bureau of Criminal Apprehension to conduct drug testing.

When asked if drug testing could return to St. Paul's unit, Assistant Chief Kathy Wuorinen said the department may look at that at some point, but now it's focused on accreditation for fingerprint comparison.

The forensic services unit has added two officers to crime scene processing to bring its total to four, Wuorinen said. It used to have three forensic scientists doing drug testing and only one doing fingerprint comparisons, but now there will be three doing the latter work, she said.

Street officers have been trained to help lab personnel when needed. Smith said the unit was also planning to hire more forensic scientists and a quality assurance manager.

"I am very confident. I want our public and our citizens to be confident in the capabilities we have in our forensic services unit," Smith said.

Nicole Norfleet • 612-710-5367

Twitter: @stribnorfleet