 This is stated in "The End of Time" when the Tenth Doctor explains to Wilfred Mott that a Time Lord can die before they have a chance to regenerate, in which case they die outright.In "The Deadly Assassin" at least one of the murders was carried out with a 'staser', possibly a weapon designed to both kill and prevent regeneration (stasers are also stated to have little effect on non-living tissue).In the Series 4 episode "Turn Left",<ref name="Turn Left"></ref> the Tenth Doctor's body is shown on a stretcher following the parallel events of "The Runaway Bride".