The prosecution points out that the gun belongs to the accused, the defence points out that the fingerprints are someone else’s, the jury nods to one another, the accused goes free.

In the case of The Port of Houston vs. Aaron Caffrey, the gun belonged to Caffrey, so his defence was, naturally, that someone else had used it without his knowledge. The prosecution explained that whoever had used it would have left fingerprints and these could not be found. The defence countered that the perpetrators could have wiped their prints immediately after use, and anyway, the investigators could never have checked every part of the gun. The jury believed Caffrey’s explanation. The only problem was that, at the outset, none of them knew how the gun worked, how it was used or how someone else could have picked it up and fired it from another part of the World.

The case highlights the continued problems of trying computer-based crimes before non-technically literate juries. Caffrey was acquitted, not because someone else had fired the gun, but on the possibility that somebody could have done so without leaving a trace of evidence. A more clued-in jury may have changed the outcome of the case but as it was, the explanations of logfiles and fractured hard disk blocks and subsequent counter-arguments proved baffling. Reasonable doubt came all too easily for the jurors, making it almost impossible for prosecutors to refute the Trojan Horse defence in future cases.