This Doesn't Feel Right

This programme (available on BBC iPlayer for a limited time) tells the worrying story of two British tourists who ran into big legal trouble when they inadvertently passed forged Euro notes, one in Austria and one in Cyprus. One forged note appears to have come from an unwise deal done in the street with a stranger, the other from Thomas Cook. I know next to nothing about foreign jurisdictions, but if it is the case that you can be convicted and imprisoned for passing a forged note without any proof that you knew it to be forged that seems to be contrary to natural justice. I am no lawyer, but I do know that most offences (apart from strict liability ones such as motoring matters) in this country need to have been committed deliberately.
Can anyone out there clarify this?