He needs to take advice because this is a serious offence.
The maximum sentence for simply possessing such images is five years imprisonment, and up to ten years if the defendant was in any way involved with making the images. The number and nature of the images is the main factor in determining the sentence but even at the lowest level (which would involve a small number of images of the least offensive kind) usually attracts a Community Penalty. In most cases those convicted also have to sign the Sex Offenders� Register. A conviction such as this seriously affects the lives of those convicted.
It is impossible to say here whether there is a realistic chance of a conviction, especially in the circumstances you describe. Your friend should seek legal advice at the earliest opportunity.