Therac-25

I’d never heard of the Therac-25, a linear accelerator used for treating cancer that killed 6 people in the 80s. AECL, the company that produced the Therac-25, took most of the hardware safety controls out of the system when they integrated a PDP-11 into the system more closely.

Then, when they did the safety analysis of the system, they excluded the software entirely from the analysis, rendering the work essentially meaningless.

Nancy Leveson has a superb overview of the Therac-25 accidents and their root causes. Required reading for anyone who has ever put too much faith in software.