SAN DIEGO -- A man who strangled his longtime girlfriend just hours after getting out of jail for beating her up was sentenced Friday to 21 years to life in prison.

Melvin Lee Carter was convicted last month of second-degree murder, false imprisonment and assault with a deadly weapon for the Dec. 17 slaying of Christina Michelle Jones, who was the mother of his two children.

A tearful Carter apologized for his actions in a courtroom filled with the victim's family members and friends.

"I love her," the 29-year-old defendant said. "I am guilty. I can never take it back. I just beg you guys to forgive me."

Jones' cousin, Jennifer Bradford -- who moved to San Diego to help Jones care for her children -- asked Carter why he did what he did.

"How dare you do this to your kids," Bradford told the defendant. "I want you to know that you've done the worst thing a person could possibly do. You deserve to suffer like no other."

Andrea Martin, the victim's twin sister, told Carter that she urged her sister to leave him.

"You strangled her. You killed me. I hate you," Martin told the defendant. "You left your kids with no mother."

Deputy District Attorney Pirrello told Judge Robert F. O'Neill that Carter subjected Jones to five to six years of violence and routinely beat her up over "silly things."

"Christina Jones did absolutely nothing to deserve to die," the prosecutor said.

Pirrello -- who had sought a first-degree murder conviction -- said the murder was not an "impulse killing," calling Carter's actions "heinous and despicable."

Carter's attorney, Debby Kirkwood, contended during the trial that her client killed the 31-year-old former stripper in the heat of passion and should be convicted of voluntary manslaughter, not murder.

Pirrello said Carter decided to kill Jones while in jail on the domestic violence charge because she wouldn't bail him out of jail for three weeks.

The day of the killing, Carter's family got him out of custody and he went straight to the Golden Hill apartment he shared with Jones and their children, Pirrello said.

Bradford and Jones came up with a plan to have Bradford meet the defendant on a street corner and give him a suitcase, cash and let him see his 16-month-old son, the prosecutor said.

But as Bradford started out the door to meet Carter, he burst in and locked the door behind him, setting off a seven-hour ordeal that ended in Jones' death.

Carter lunged at Bradford with a knife and swung a frying pan at Jones and Bradford, but missed, the prosecutor said. At some point, Jones decided to lock herself in a bathroom so she could call 911, which irritated the defendant, Pirrello said.

He said Bradford made a break for the front door and called 911. At the same time, Jones got through to 911, but Carter broke in and strangled her, Pirrello said.

Carter's children -- including his 5-month-old daughter -- were sleeping and did not witness the ordeal, according to Kirkwood.

But Pirrello said the children were in the room when their father first arrived and witnessed Carter swing the knife and frying pan at Bradford.

The defendant was in the military when he met Jones, who was a stripper at a local club, Kirkwood said. Carter begged her to stop dancing and she told him she would, which became a point of contention, according to the defense attorney.

Carter was arrested in November 2007 for punching Jones in the face. The defendant pleaded guilty and was placed on three years probation. He was arrested again in November 2009 when Jones told police he had hit her a week earlier.