steven drizin is a clinical professor at northwestern university's pritzker school of law. >> so, in its purest form, the felony murder rule means that if you commit a felony, and, during the course of that felony somebody dies, you can be convicted of first-degree murder-- the most serious crime on our statute books-- even if youll didn't intend to he person who died, even if the death was accidental. >> reporter: 42 states ha some form of a felony murder rule, and it's interpreted differently in each. in some cases, it's been used to charge accomplices with murder. so, for instance, if two people rob a store and one of them kis the clerk, both of them are charged with murder. the idea is, everyone involved in a felony should be held accountable fothe consequences. but some states interpret felony murder more broadly. in rare cases, if the clerk kills one of the robbers, the other robber is charged with murder. take the case of justin doyle in in 2008, doyle, 15 and unarmed, set out to robe with three other boys. they thought it was empty.ng a person stayi there shot and killed one