LOUISVILLE — Former state lawmaker Steve Nunn pleaded guilty today to murder for shooting his ex-fiancee and was sentenced to life without parole, his attorney said.

Nunn, 58, the son of former Kentucky Gov. Louis B. Nunn, faced a potential death penalty if his case had gone to trial in August for the death of Amanda Ross, 29, who was shot outside her Lexington townhouse on Sept. 11, 2009.

Nunn entered the guilty plea before Judge Pamela Goodwine in Fayette Circuit Court in Lexington, according to his attorney, Bette Niemi of Louisville.

Niemi said Nunn, of Glasgow, also pleaded guilty to violating a domestic violence order. Ross had obtained the order against him before her death.

Ross’ slaying prompted Kentucky lawmakers last year to enact Amanda’s Law, which allows counties to use GPS tracking devices in domestic violence cases.

Dale Emmons, a political consultant and Ross family spokesman, said the plea came as a surprise.

“The guilty plea was not expected, especially after the last court hearing,” Emmons said. “But, it’s one the family thinks is just.”

Nunn was arrested the day Ross was found shot dead. Police said he was apprehended in a cemetery in Glasgow where his parents are buried, with blood on his shirt and wounds to his wrists, and he was pointing a gun to his abdomen while talking to someone on cellphone. Police said he fired off one shot before being arrested.

Niemi said negotiations on the plea deal have been ongoing and a deal was reached late last week.

A telephone call to Fayette Commonwealth’s Attorney Ray Larson was not immediately returned.

Amanda’s Law was the result of work by Amanda Ross’s mother, Diana Ross, who consulted closely with House Speaker Greg Stumbo to get the legislation passed.

Emmons said the family had no objection to the plea and life sentence because it brings the case to an end months sooner than anticipated.

“It did come to fruition quicker than we anticipated,” Emmons said. “This has not been quick, though. The family has been going through this for months.”

Diana Ross did not address the court during the hearing, because she was unprepared for the plea, Emmons said. Emmons said Goodwine allowed her to submit a victim impact statement in writing into the court file, something that will be done in the next few days.

“We think it’s a just verdict. The plea gives the family an opportunity to get on with their lives,” Emmons said. “We said when Amanda was murdered we wanted justice. We feel like we now have it.”

Stumbo said in a statement he hoped the plea would give closure to the Ross family. He also said he will continue to encourage state courts to make use of Amanda’s Law.

“I strongly encourage courts to use this law in the appropriate situations, because it’s now clear that it could have made a difference for Amanda,” he said.

Steve Nunn, a Republican, had made a name for himself in Kentucky politics, spending some 15 years in the state legislature and making an unsuccessful run for governor in 2003. He failed to win re-election to the state House in 2006.

He had been serving as deputy secretary of the Cabinet for Health and Family Services, but was put on administrative leave and then resigned after he was charged with domestic violence against Ross, with whom he had lived for several months. Under a protective order obtained by Ross, Nunn also was prohibited from possessing firearms.