Can a brain scan uncover your morals?

Brains images are becoming standard evidence in some of the country's most controversial and disturbing death penalty trials - including the case of Steven Northington

It's hard to imagine Steven Northington killing two people. The 43-year-old says he likes to make people laugh, "like a comedian". He's a loyal son to his troubled mother and father. He sends his younger sister birthday cards from prison and draws elaborate smiley faces on them. His defense team laughs with affection when they hear his name because he is, they say, "a character".

Between 2003 and 2004, Northington was slinging for a drug ring that flooded his Philadelphia neighborhood with bloodshed. The Kaboni Savage Organization was responsible for nine murders during those two years alone, including the firebombing of a house that killed two women and four children.