Right I've been thinking about the special defence. I think the accused may have been advised to go for this to sow some seeds of doubt in the jury's heads - probably his only chance of getting off with it. Coming from the defences point of view an unrelated person in close contact with the child who is known for dealing drugs was watching *advertiser censored* at night just metres away from the child, it does sound a bit dodgy.
My worry is that the forensics are perhaps weak and this defence could work.