This law covers possession of any extreme image, regardless of how it is depicted – print, film, or electronic.
Print and film are fairly unambiguous. It is electronic versions that are likely to give rise to trouble, because of the ambiguous and often hidden nature of the cached copies or log files created by electronic gadgets, often without the knowledge of the consumer.
Advice prepared for Backlash in the run up to the legislation coming into force in January 2009 ensuring that a personal computer and similar devices are divested of any borderline images can be found here.
The Government’s own advice says this about Possession in the section on Defences.
“That the person was in possession of an extreme image but had not looked at it and therefore neither knew, nor had reason to suspect that it was an extreme pornographic image; this will cover those who are in possession of offending images but are unaware of the nature of the images for example, where a person is sent an electronic copy of an image which he saves without looking at it and which gave rise to no suspicion that it might be extreme pornography.
That the person had been sent the image without having asked for it, on their own behalf or through someone else, and, having looked at it had not kept it for an unreasonable length of time. This will cover those who are sent unsolicited material by any means and who act quickly to delete it or otherwise get rid of it.
What constitutes an unreasonable amount of time depends on all the circumstances of the case.
Case law supports the view that, in normal circumstances, deleting images held on a computer is sufficient to get rid of them, i.e. to divest oneself of possession of them. An exception would be where a person is shown to have intended to remain in control of an image even though he has deleted it – that will entail him having the capacity (through skill or software) to retrieve the image. Porter  WLR 2633.”
Further discussion on Porter can be found here.
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