As a longtime St. Paul police officer and former gang investigator, Ruby Diaz knew that her fellow cops would never approve of her dating a felon.

When she first did so, back in the early 2000s, she said her colleagues turned on her in the worst possible way — following her in unmarked cars, flooding her vehicle with lights and refusing to back her up on the beat.

That's why, the 38-year-old cop testified Thursday at the close of her forgery and identity theft trial, she decided to use a friend's identity earlier this year to wire her new boyfriend — a felon and 16 years her junior — $1,500 in prison.

"When my co-workers found out" about the earlier relationship, she said, "it became hell at work. I would get dispatched to calls, and I wouldn't get backup."

Diaz is on trial in Ramsey County District Court on two counts of aggravated forgery and one count of identity theft for transactions involving Ramone D. Smaller, a purported gang member who is serving six years in prison for attempted murder. Diaz said she first met Smaller when he was a 12-year-old student, and fell for him romantically when he turned 21 last year.

Diaz also testified that a picture of her previous boyfriend and a picture of her personal car, which he sometimes drove, were posted in the department's roll call room with instructions "to stop the vehicle and give no breaks."

St. Paul police Sgt. Paul Paulos, a department spokesman, said that he was not aware of any previous internal investigations into the claims Diaz made in court.

"This is the first time the department has been approached with these allegations that I believe of," Paulos said.

It's unclear if Diaz's testimony will prompt an internal investigation, but Paulos said that "anything is possible."

A handful of St. Paul police officers listened to her testimony, including the head of the department's internal affairs unit.

Assistant Hennepin County Attorney Andrew LeFevour, who is prosecuting the case because of a conflict of interest in the Ramsey County attorney's office, told jurors in his closing arguments Thursday that Diaz took "calculated" steps to hide her identity by using her friend Mao Lee's name, birth date and home address to create an e-mail address and accounts with the Minnesota Department of Corrections and Western Union.

The purpose of her deception, LeFevour said, was to place herself in the "shadows" of the financial transactions. At a glance, records of deposits into Smaller's prison account would show Lee's name and information. Only if authorities dug deeper, LeFevour said, would they discover that the money was coming from Diaz's bank account and credit card.

Diaz's attorneys, Sam Savage and William Bulmer, said their client's case was about intent. They said that she never intended to defraud Corrections or Western Union, or misrepresent herself as Lee.

Although Diaz admitted to using Lee's information, Bulmer told jurors, she also used her own home address for billing, her own bank and credit card accounts, and her own cellphone number as a backup contact.

Diaz also made the transactions using her cellphone and work-issued computer, he said.

"She simply did not want to be harassed, and that's why she did what she did," Bulmer told jurors.

'You're too young'

Diaz was working as a school resource officer at Humboldt High School when she first met Smaller, then a seventh-grader. Diaz worked at the school, which includes middle and high school grades, for several years. She is on paid administrative leave pending the outcome of her trial.

Diaz testified Thursday that she first got to know Smaller, now 22, when a teacher recommended that the two connect. Smaller was looked upon as a leader by other students, and the teacher thought he could be a good influence if Diaz earned his trust.

Diaz said that she, the teacher and the teacher's aide served as Smaller's mentors in his troubled world.

Smaller drifted in and out of their lives, Diaz testified, and resurfaced in April 2013. Sometime after that, she said, he told her he was romantically interested in her and always had been.

"I told him, 'You're too young. I can't go there,' " Diaz testified.

Undeterred, Smaller waited until he turned 21, she said, and approached her again.

"I said, 'Well, let's see what happens,' " Diaz testified.

Diaz said that, with Smaller, she wanted to settle down, get married and have children for the first time in her life.

"As naive as it may seem, yes, I did," she said.

But memories of her co-workers' reactions to her relationship with the felon in the early 2000s haunted her, she said. She worried about how her co-workers would receive news that she was dating Smaller, who remains charged with 10 felonies for violent drive-by shootings in 2013, and two felonies — aiding an offender and crime committed for the benefit of a gang — for a 2012 incident.

"I got tired — I'm tired of being scrutinized for my personal life," said Diaz as she wept on the witness stand. "It's not my department's business. … It's not!"

Jurors began deliberations about noon Thursday and will resume Friday morning.

Chao Xiong • 612-270-4708

Twitter: @ChaoStrib