St. Paul police secretly obtained a DNA sample last year from a fellow officer who was dating a purported gang member under investigation for three shootings.

Sgt. Tim McCarty testified Thursday in Ramsey County District Court that he instructed a commander to retrieve a drink bottle used by officer Ruby Diaz in February 2014 at a meeting in a West Side community center. Diaz was dating Ramone D. Smaller at the time, a purported gang member who is on trial this week on 10 felony counts in shootings in late October 2013.

Sam Savage, one of Diaz's two attorneys, said McCarty's testimony was the first he had heard about the DNA-gathering.

"It just goes to show the level of harassment she was under at the [St. Paul Police] Department," said Savage, adding that he does not believe that Diaz was aware of it, either.

Diaz, 39, began dating Smaller, 22, in 2013. She was convicted in December of identity theft for using her friend's information to send him $1,500 last year while he served a six-year prison sentence for attempted murder.

Diaz, who was a school resource officer at the time but has worked as a gang investigator, was fired after her conviction.

DNA samples were collected from several individuals to compare with samples collected from a handgun recovered in January 2014 in a car Diaz had rented for Smaller at the time of the shootings.

Assistant Ramsey County Attorney David Miller asked McCarty if he had collected a swab kit from Diaz, which is typically obtained by swabbing a person's inner cheek for DNA. The samples are often collected by executing a search warrant.

"It wasn't appropriate," McCarty said of following that protocol for Diaz.

McCarty testified that he instructed a commander to attend the meeting last February, watch Diaz and collect whatever bottle she disposed of. He testified that he delivered the bottle to the Minnesota Bureau of Criminal Apprehension (BCA) for testing.

Miller asked if he labeled the sealed bag containing the bottle with Diaz's name.

"I did not," McCarty said, adding that he labeled it "known sample from an unnamed person."

Attorney Savage said that while the department's actions do not violate lawful search and seizure, they are "concerning."

"Presumably, if the police had wanted to, they could've gotten a search warrant for a DNA sample, and [Diaz] would've complied with a court order," Savage said. "And the fact that they didn't do that is questionable, to say the least."

Testifying at her trial in December, Diaz sobbed and said that when she had dated a different felon before Smaller, officers had followed her in their cars and had refused to back her up on calls.

The Police Department did not comment Thursday about collecting Diaz's water bottle.

BCA forensic scientist Allison Dolenc testified Thursday that Diaz's DNA was not found on swabs of the gun police believe was used in the shootings. Smaller was the predominant DNA contributor to swabs of the gun's grip and trigger, which also contained a DNA mixture of three or more people, Dolenc said.

No one was injured in the shootings.

Testimony resumes on Tuesday.

Chao Xiong • 612-270-4708

Twitter: @ChaoStrib