A criminal psychologist believes Australia's mushroom-lunch murderer's appeal is totally predictable

Erin Patterson was sentenced to a minimum of 33 years in prison for murdering three former inlaws - by lacing a beef Wellington with death cap mushrooms.

Her legal team filed an appeal on Monday.

Psychologist Tim Watson-Monroe says she's been kept mostly in isolation, and has nothing to lose.

He says for her it's an academic position, because she'll be in her 80s before eligible for parole.