It is your responsibility to purchase the correct ticket. If you buy it from
a machine you must have a valid discount card at the time of travel. If it
expired it doesnt matter how long ago....its expired. There are a number of
criteria for a young persons railcard....perhaps your friend no longer meets
them. How many days is...'just a few'?
Its like an adult buying a child ticket....its not valid.
Is it possible your friend somehow antagonised these guys......

However....it does seem a huge over reaction to this minor infringement. But
remember they probably get lots of people saying they didnt know it just
expired etc etc all the time.
Its unusual to get the police involved unles there was something else that
made them question that deeply.
I think you should clarify with your friend exactly what happened, 'He was
chucked out at Kentish Town and questioned in "Special" room', sounds very
dramatic. Perhaps a slight exageration in the heat of an angry phone call?

If its his first time caught he will probably get a letter saying they
thought about it and decided its in no ones interest to prosecute. 2nd
time....they will prosecute and its up to a judge.
Conviscation of tickets? The small print says its belongs to them at all
times and if they want they can take it if you are not fulfilling the terms
of the contract you both entered into.

The penalty fare system is not for people who have purchased a ticket
without the valid cards...its for no ticket/wrong ticket situations. By
purchasing a ticket that he isn't entitled to...sorry but its classed as
fraud.

No i dont work there. I travel on it.....and frankly i'm fed up with people
free loading......if we all paid up then perhaps we could get a decent
service etc.

Mal