False and tainted evidence will be central to David Tamihere's final attempt to clear his double murder conviction

His appeal's begun before the Supreme Court today.

Tamihere spent almost 20 years in jail for killing young Swedish tourists Urban Hoglin and Heidi Paakkonen in 1989.

Lawyer Murray Gibson says he'll present claims on fair trial grounds, with seven breaches relating around incorrect prison and witness evidence.

A Court of Appeal found evidence from a jailhouse snitch amounted to a miscarriage of justice, but didn't justify setting aside the convictions.

They include false claims Tamihere stole a watch from one of the victims.