Newcastle back rower Mitch Barnett has been suspended for six matches at the NRL judiciary for raising his forearm and collecting Penrith forward Chris Smith in an off-the-ball hit.

Barnett was sent off in the Knights' 38-20 loss to the Panthers in Bathurst on Saturday and was referred straight to the judiciary on a dangerous contact charge.

He pleaded guilty at the judiciary on Tuesday night.

The NRL argued for an eight-match suspension, while Barnett's lawyer Nick Ghabar pleaded for a four-match ban.

The judiciary panel — consisting of Geoff Bellew, Bob Lindner and Tony Puletua — deliberated for 32 minutes, before handing the 27-year-old his suspension, saying his behaviour was reckless but not intentional.

"I am just hoping Chris is alright, we've exchanged text messages," Barnett said after the judiciary hearing.

"I'm disappointed and I'll go away and do my time.

During the hearing, Barnett said he only saw Smith late and put out a "bumper" to protect himself.

He said he only noticed Smith in his peripheral vision as he was focused on stopping the Panthers spreading the ball to the flank to score a try.

"I have a duty of care to opposition players and I understand that," Barnett said.

"It was careless but I never intended to lift my arm that high."

Smith has not been named in Penrith's round-four match against South Sydney, while Barnett will not be able to play for the Knights until round 10 when they face Canterbury.

AAP