An approach to quantifying the plausibility of the inadvertent download defence

Abstract

A table of 95% confidence limits on the probabilities for randomly downloading relatively small numbers of illegal images or sensitive documents amongst a relatively large number of other images or documents has been computed. It is anticipated that these data will assist prosecution officials in arriving at a decision as to whether or not there is a reasonable likelihood of a successful criminal prosecution when the inadvertent download defence is employed in cases of possession of child pornography, terrorist material or espionage-related documents. The same data can also be used by defence counsels to assess the strength of the prosecution's case.

Cosmic rays

“…The first Trojan Horse Defence (THD) [34,35] was successful at least in part because its low plausibility was not appreciated with any degree of certainty at the time of the trial; however, subsequent quantitative analysis based on complexity theory was able to attach probabilities to each of a number of different THD scenarios [36]. The putative Inadvertent Download Defence (IDD) against the possession of small quantities of child pornography has also been analysed quantitatively using statistical Urn methods to determine its plausibility with numerical data from two actual cases that ultimately did not go to trial [37]. The present contribution is another example of proactively analysing a putative novel defence stratagem in order that it is well understood before it is offered at a trial, unlike the original THD.…”

Quantitative evaluation of the results of digital forensic investigations: a review of progress

“…[0.03%, 2.54%] and ca. [0.00%, 4.35%], respectively [ 30 ].…”