[Jack Simth]

It's hard to say if it is a myth or not, between the placebo effect and the note that the injection location is missing from the story. The brain controls a lot - if he truely believed he was going to die, he could have (especially as by the time many death row inmates reach the execution chamber anymore, they are old enough for heart attacks to be a serious risk). Injected into the right (wrong?) place, water could harm you - water injected into the spine (called a spinal tap) interferes with nerve function, and blocks pain. Injected into a place where it would interfere with the nerves going to the heart, and it might be able to stop a man's heart that way.