Computer systems are increasingly relied upon for a wide range of important tasks, but much of the research on reliability has been restricted to the control systems for safety-critical hardware. For other systems, efforts to assess their effectiveness has been more ad-hoc and of questionable validity, even those relied upon to produce legally admissible evidence. From breathalyzers and forensic software to the infamous Post Office Horizon system, computer bugs can make the difference between someone being imprisoned and going free. This talk will discuss some examples of computer evidence failures risking causing miscarriages of justice, and what can be done to mitigate such risks in the future. In particular, it will motivate the idea that computer systems relied upon for computer evidence should be built with rigorous engineering techniques, but that these techniques are distinct from what are needed for safety-critical systems. When combined with appropriate treatment by the legal system, we can help avoid future miscarriages of justice.