A St. Paul man admitted in court Thursday that he fatally shot his longtime partner but quickly backtracked and said his shotgun unexpectedly slid into his trigger finger.

"I didn't think it would go off," John G. Weisner Jr. said during his plea hearing.

Ramsey County District Judge William Leary ultimately accepted Weisner's guilty plea after several rounds of questioning.

Weisner, 56, pleaded guilty to second-degree murder with intent in the Sept. 17 shooting of Ramona Turner, his partner of 40 years.

Weisner said that he shot Turner, 54, after a night out drinking with her, their two grown sons, one of the son's girlfriends and a male friend.

Weisner and Turner returned to their home in the 100 block of E. 6th Street between 12:30 and 1 a.m. He went to sleep in the bedroom, and she lay down on a love seat, where she had been sleeping since telling Weisner she was leaving him.

Weisner testified that he awoke when he heard Turner talking on the phone with the male friend from the bar. The two had a flirtatious relationship, he said.

Weisner said he retrieved shotgun shells from the basement and loaded two of them into the gun in his bedroom.

He shot Turner, he testified, in front of one of their sons and was going to shoot himself when the son intervened. Weisner stabbed himself several times with a knife instead.

Then, Weisner began tiptoeing around his guilt, prompting Leary to intervene and Assistant County Attorney Janice Barker to ask a second round of questions.

Under questioning from Leary, Weisner said he was cocking the gun when it slid into his trigger finger and fired.

Were you intending to shoot Turner? Leary asked.

"At that time, I don't know," Weisner said. "It happened."

Barker asked Weisner whether the gun was pointed at Turner, and whether a shotgun shell would follow the path of the barrel.

Yes, he said.

Barker asked whether he pulled the trigger.

No, he said.

"The trigger doesn't go off on its own," Barker said.

Weisner again tried to convince the court that the gun slid into his trigger finger.

Weisner's plea was accepted after further questioning from his attorney, Erik Sandvick.

Weisner agreed to a middle-of-the-box prison term while acknowledging that the judge can hand down any amount of time within guidelines.

Sandvick said that given Weisner's criminal history score of zero, the presumptive range is 21¾ years to about 30½ years, with 25½ years as the midrange point. He is scheduled to be sentenced on March 8.

A son at Thursday's hearing declined to comment.

Chao Xiong • 612-270-4708

Twitter: @ChaoStrib