The Law Commission presumption concerning the dependability of computer evidence

An invited paper

  • Peter Bernard Ladkin
  • Bev Littlewood
  • Harold Thimbleby
  • Martyn Thomas


In this paper Peter Bernard Ladkin, Bev Littlewood, Harold Thimbleby and Martyn Thomas CBE consider the condition set out in section 69(1)(b) of the Police and Criminal Evidence Act 1984 (PACE 1984) that reliance on computer evidence should be subject to proof of its correctness, and compare it to the 1997 Law Commission recommendation that a common law presumption be used that a computer operated correctly unless there is explicit evidence to the contrary (LC Presumption). The authors understand the LC Presumption prevails in current legal proceedings. They demonstrate that neither section 69(1)(b) of PACE 1984 nor the LC presumption reflects the reality of general software-based system behaviour.

Index words: Law Commission; presumption computers are reliable; software impossible to be correct