Shae Brider, who served a prison term for manslaughter, is through to the next round of X Factor.

X Factor producers knew of a contestant's violent past, but say the show offers him a second chance.

Shae Brider was sent to bootcamp by the judges following his reggae rendition of Eminem's The Real Slim Shady on the show last night.

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But it was his past which raised a few eyebrows.

In his introduction before his performance, he mentioned the fact he went to prison for six years but made it seem as though it was a matter of wrong place, wrong time for him.

"I met some dudes and we went to a bonfire...there was a commotion with two of them and one of them stabbed the other one and he ended up passing away."

But reports from his court cases paint a different picture.

Several court cases heard how Brider, Rawiri Hatata, Rio Hartley and Jordan Aranui went on a violent spree in Whanganui on Guy Fawkes night 2004, attacking four people in total.

Hatata, then 17, stabbed 16-year-old Jeremy Frew through the heart at Castlecliff Beach and was jailed for life with a minimum 10-year non-parole period for murder.

Brider was originally convicted of manslaughter in 2006 but the Court of Appeal set aside the conviction and he was retried in May, 2009.

The second trial saw him again convicted of manslaughter and the evidence increased his share of the blame.

Justice Joe Williams said although it had not been shown that Brider was involved in punching Frew, he formed part of the group of attackers and was standing close behind the youth with the knife right before the stabbing.

Brider had heard one of the group bragging earlier in the night that he wanted to stab someone, and he went along with the group anyway.

The group had already attacked another man, Daniel Grey, who suffered a broken jaw.

After Frew was fatally stabbed the four teens went on to stab another man in the back at a petrol station.

After Brider's first trial, Detective Sergeant Stu Nightingale said in 19 years in the police he had never seen a night like the one that claimed Frew's life.

"It's been described as a senseless killing and I'd have to agree," he said.

"For one set of offenders to go around like that...what on earth went through their minds?"

After the second trial, Frew's mother, Donna Travers, said none of the group had ever shown remorse for the killing of her son.

A MediaWorks spokeswoman said Brider disclosed his criminal record when he entered The X Factor NZ and as a standard part of the process a police check was run.

"It was important to include this part of Shae's background in last night's episode, and as is the case with all contestants, this was done in his own words," she said.

"The X Factor NZ acknowledges the impact Shae's past actions have had on his victims, and apologises for any distress that has been caused by last night's episode.

That was not our intention. However it is important to note the NZ Justice system judges Shae has paid his debt to society, and now has a second chance to make a positive contribution."

Footage of performances, including Brider's, from last night's show were not playing on the TV3 website this afternoon.