AP Explains: Why ex-NFL star's conviction was erased

The ruling this week by a Massachusetts judge erasing Aaron Hernandez's murder conviction has angered the victim's family and roiled prosecutors.

It also raises questions about how the legal principle on which the ruling was based is applied.

Hernandez was appealing his conviction in the 2013 killing of Odin Lloyd, a semi-professional football player.

Hernandez was found hanging in his prison cell last month, days after being cleared of murder charges in another case. His death was ruled a suicide.

Legal experts say the doctrine of abatement holds that a conviction isn't absolutely final until an appeal is heard.

Most federal appeals courts have upheld the doctrine, but not all states adhere to it.

Legislation proposed by Middlesex District Attorney Marian Ryan before Hernandez's death calls for ending the practice in Massachusetts.