A man who killed his girlfriend because he thought she was having an affair was jailed for six years today.

David Craigie repeatedly hit Sonya Todd, 21, with a dog chain during the prolonged assault at their home in Methil, Fife.

The attack, which is believed to have lasted up to five hours, left the young mother with so many injuries that pathologists were unable to count them all.

Craigie, 24, was initially charged with murder but pleaded guilty at an earlier hearing to the reduced charge of culpable homicide, in light of evidence that Ms Todd's diabetes was a factor in her death.

At the High Court in Edinburgh today, Lord Kinclaven gave him an extended sentence of six years behind bars to be followed by three years' supervision.

The judge told Craigie: "You have demonstrated you are capable of serious violence."

He said: "The fact remains that this was a sustained assault upon Sonya Todd, a young woman who was 21, who seemed not to have fought back.

"The consequence, albeit unintended and unforeseen, was the tragic loss of a young life."

Ms Todd's relatives were in court today to see her killer being led away to the cells.

But her father, George Todd, said the sentence could have been longer.

He said: "Six years, to me, is kind of short for anybody's life. "It doesn't matter whether it was culpable homicide or murder, I still think it's a short sentence."

Mr Todd, 57, also questioned the decision to accept a plea to the reduced charge, in light of the injuries his daughter suffered.

"For the sustained battering that she's taken, there's no way it should have been culpable (homicide)," he said.

"We've not got to see the pictures, but they say they're that bad that they don't want us to see them.

"I just don't know why it came down to culpable homicide instead of murder."

Mr Todd described his daughter as having been a "just an ordinary teenager" with a "happy-go-lucky" nature before she knew Craigie.

But that changed when she got involved with him, her father said.

"Everything changed, she wasn't the same lassie. She didn't get to have her own pals or anything."

The court heard that the pair had a volatile relationship which could turn violent when they argued.

Craigie launched his brutal attack after accusing the mother-of-one of cheating on him with a man who worked at a local car wash - claims her family have dismissed.

He even scrawled his accusations on her arm on the night of the attack on March 23 this year.

The court heard how neighbours were woken by a disturbance shortly after midnight and the noises continued periodically until about 5.30am.

Her body was found by a neighbour, who also found Craigie with tears streaming down his face. He said: "I think I've killed her."

Craigie later told police: "I love her from my heart. Doesn't matter of the circumstances, if you kill somebody you kill somebody."

He added: "I can't believe she's dead. I left a wee lassie without a mum."

Craigie admitted repeatedly striking Ms Todd with a dog chain, as well as scratching, biting, punching and kicking her during the lengthy ordeal.

Defence QC Mark Stewart said his client was remorseful about what had happened.