Therac-25 Lawsuit for Victims Against the AECL Zeke Dunlap Quinncy Thomas Sterling Sanders

Therac-25 Victims The Therac-25 software is directly to blame for the injures to six victims between 1985 and 1987. The Atomic Energy of Canada Ltd. (AECL) carries the burden of blame for the massive overdoses of radiation that the Therac-25 gave to patients being treated by the software. Three deaths were caused by this unimaginable lapse in judgment by the AECL.

Whose to blame? The AECL did not take the appropriate measures to insure that the Therac-25 would provide the utmost safety precautions for the patients who were being treated with the software. Insufficient testing, numerous bugs, bad safety design, and poor programming techniques were all contributors to the incidents that injured patients who trusted the Therac-25.

Design Flaws in the Therac-25 The software developers were too cheap! The Therac-20 has independent protective circuits for monitoring electron-beam scanning, plus mechanical interlocks for policing the machine and ensuring safe operation. Too avoid extra expenses, AECL decided not to duplicate all the existing hardware safety mechanisms and interlocks. . Error messages were not informing to the operators of the software. There were no definitions found in the manual that came with the Therac-25. The Therac-25 basically had reused software. This was discovered when bugs found within the previous model of the Therac-20 was also found in the Therac-25..

Bug in the Therac-25 A major bug in the Therac-25 was an overflow error, which could have been prevented if careful design techniques would have been implemented. The overflow error checked off that the system was ready to begin radiation, when the system was actually giving harmful doses of radiation to the patients.

AECL’s Tenacity The AECL repeatedly stated that there was no possibility of an overdose of radiation that could be caused by the software. After the 2nd incident, the AECL told the FDA that the source of the problem could not be located, but the AECL publicly stated that the safety of the Therac-25 had been improved by 5 times after they implemented some safety features in reaction to the incident. A Canadian agency urged the AECL to implement more safety features, but the AECL insisted that the software was now safe.

Overconfidence Some hospitals using the Therac-25 implemented their own safety mechanisms. Those hospitals never had a single overdose of radiation on any patients. Other hospitals felt secure when the AECL told them it would be a waste of money to implement safety mechanisms because the software was safe.

Conclusion The AECL’s irresponsibility should not be overlooked. The victims of the Therac-25 should not be left without some retribution. The AECL’s lack of emphasis on the safety of the software is extremely tragic in such a safety critical software system.