When DNA analysts examined blood evidence from the Baltimore County townhouse where Anna Marie Bergman was shot to death, they isolated a genetic profile of not only the 20-year-old murder victim. Mixed with her blood, they also found DNA of her 3-year-old son.

"It was probably tears," prosecutor Michelle Samoryk told a judge yesterday at a plea hearing in the case.

Ryan J. Butler Sr., 22, of Baltimore was sentenced to 50 years in prison after pleading guilty to first-degree murder. He was convicted of shooting his former girlfriend three times - including twice in the head - in front of their son and then snatching the young boy.

Butler was arrested minutes later after a police officer familiar with the couple from previous calls to the home put out a radio alert for Butler's car.

The relationship between Butler and Bergman was marked by issues of control, the prosecutor said.

As a high school student, he demanded that she call him before, during and after school, Samoryk said. Letters from Bergman to her boyfriend were filled with assurances that she was not cheating. And she at least once suggested that she would no longer tolerate his physical abuse, the prosecutor said.

Bergman eventually moved out of the apartment in Southwest Baltimore that she had shared with Butler and her son.

"Once they broke up, he became increasingly obsessive," Samoryk told the judge. "Ultimately, the defendant couldn't stand that he wasn't with her anymore."

On July 27, Butler showed up at Bergman's home and threatened to kill her and their son.

The woman called police. She tried to get a protective order. She went away for the weekend with her son, the prosecutor said.

Still nervous when she returned home Sunday night, Bergman called her brother, who came over with his girlfriend and spent the night. The couple left the next morning at 5 o'clock to go to work.

At 7:45 a.m. July 30, Butler returned.

Bergman was dead when police arrived, responding to a report of gunfire.

"Unfortunately, it was almost a textbook domestic violence murder," the prosecutor said.

Defense attorney Peter S. O'Neill asked the judge to consider the psychiatric evaluation of his client in which a doctor found that Butler suffered from a major depressive disorder with psychotic features.

He expressed disappointment that Butler had never received the help he obviously needed - including after he attempted suicide just a week before the shooting.

Asked whether he wanted to say anything before he was sentenced, Butler shook his head. Bergman's friends and family members began to sob.

"I'd just like to apologize," he said.

Calling the killing a tragedy for both families and most of all for little Ryan Butler Jr., Baltimore County Circuit Judge Dana M. Levitz sentenced the defendant to life in prison, suspending all but 50 years of the term.

jennifer.mcmenamin@ baltsun.com