A US biologist is to face life in prison without parole for murdering three colleagues and wounding three others in a 2010 shooting spree.

A jury deliberated for about 20 minutes before convicting 47-year-old former University of Alabama, Huntsville, scientist Amy Bishop.

The woman reportedly opened fire at a faculty meeting after being denied tenure in her department.

Reports say she avoided the death penalty by pleading guilty earlier in September.

Before the plea deal, Bishop's lawyers had planned to argue an insanity defence for the 12 February 2010 shootings.