Doc has been involved with illegal and criminal enterprises (albeit as a means to obtain items for his inventions he could not purchase legally) but he is naive and care-free about the consequences of his actions. He excitedly tells Marty how he cheated Libyan terrorists out of stolen plutonium : "They wanted me to build them a bomb, so I took their plutonium and, in turn, gave them a shoddy bomb casing full of used pinball machine parts!"