Ramsey County prosecutors want to prohibit questions about a St. Paul police officer's suspension for mishandling evidence when the officer testifies in the murder trial of Jeffery Trevino.

Officer Brian Mefford was suspended for a day without pay for actions unrelated to the Trevino case, according to a memorandum filed Friday by Assistant Ramsey County Attorney Andrew Johnson.

Prosecutors plan to file a motion on or near Sept. 16, the trial's start date, to prohibit defense attorney John Conard from questioning Mefford about his infractions. Trevino, 39, is charged with killing his wife, Kira Steger, 30, who went missing in late February and was found dead three months later in the Mississippi River. The St. Paul couple's relationship was rocky, and Steger wanted to leave her husband, according to charges filed against Trevino.

Mefford worked in the St. Paul police crime lab and helped examine Steger's car at a Mall of America ramp, according to the memorandum.

The car was allegedly driven to the mall and abandoned by a suspect matching Trevino's description, according to surveillance video and GPS data. Blood matching Steger's DNA was found in the car.

According to the prosecution's memorandum: A Dec. 13 internal affairs report shows that Mefford mishandled evidence twice and misplaced a department gas credit card. He stored seven files in a bin in the crime lab for two to three months, violating department procedures, and "improperly stored evidence (a magazine and ammunition) in his desk … after it was delivered to him without proper paperwork."

Mefford also lost track of a company credit card for two weeks and did not write a report about the misplaced card as he was instructed to do.

"Investigators subsequently found the card in an envelope on a bookshelf in the crime lab," Johnson's memorandum says.

It adds that Mefford's credibility can't be attacked via cross-examination by the defense unless his conduct showed signs of untruthfulness.

"Officer Mefford failed to write some reports in a timely manner, and he stored some evidence improperly — though in all cases the evidence was still stored inside the secure crime lab," Johnson's memorandum says.

"These incidents probably delayed some investigations, and they might have created a risk that some evidence would be misplaced, but none of the incidents had anything to do with untruthfulness. The incident involving the credit card didn't even involve evidence handling."

Police records show that Mefford was certified as an officer with the department in 2001, assigned to the crime lab in 2008 and reassigned in March to the Central District. He was suspended for a day on April 2 by Assistant Chief Kathy Wuorinen for the 2012 internal affairs report. His file includes six letters of thanks or commendation.

Conard did not return a call seeking comment.

The police crime lab came under fire in 2012 for a host of problems with its drug analysis, leading the department to let go of the three civilian criminalists who tested suspected drugs.

A court hearing in Dakota County last year revealed that the criminalists were poorly trained, that sworn personnel who oversaw the lab were not familiar with the latest scientific standards and that basic scientific procedures were being ignored.

The city spent $1 million to revamp the lab, which held an open house Thursday to showcase new equipment. A civilian manager was hired in June, and the lab — now called the forensic services unit — hopes to become accredited in two years.

Chao Xiong • 612-270-4708

Twitter: @ChaoStrib