A Deadly Line of Code

The Therac-25 incident is a tragic example of how software flaws in safety-critical systems can lead to fatal consequences. Between 1985 and 1987, this radiation therapy machine delivered lethal overdoses due to software bugs and inadequate safety features. The incident highlighted the dangers of relying heavily on software without sufficient hardware safeguards, poor error reporting, and insufficient testing—especially for rare, complex scenarios.

From a quality assurance viewpoint, it underscored the necessity of rigorous testing, robust fail-safes, clear user feedback, and strong consideration of human factors in design. The Therac-25 tragedy remains a crucial lesson that software quality isn’t just about functionality—it’s about protecting lives.