Serial killer Ivan Milat will spend the rest of his life without freedom and also without the little finger on his left hand after he severed the digit with a plastic serrated knife.

Milat, who is serving a life sentence at the Supermax facility inside Goulburn jail for the murder of seven backpackers, calmly handed the finger to prison guards inside an envelope padded with newspaper on Monday.

The 64-year-old had addressed the envelope to the High Court of Australia.

"He was going to try and post it, but then of course, when you cut a finger off it does hurt," NSW Corrective Services commissioner Ron Woodham told Macquarie Radio on Tuesday.

"He got crook and it was hurting and ... very painful and of course he had to raise attention to it and hand it over."