If MtGOX were liquidated by the court instead, the 200'000 BTC would be split between J and M according to their deposits and withdrawals, which are much harder to doctor since they can be checked against bank records and the blockchain. So perhaps J would get most of the 200'000 and M would get close to nothing.
In other words you don't believe there will be a criminal investigation to discover where the BTC went. The court doesn't care about whether a deposit is real or not. Why not?
BTC deposit records are the easiest to alter by recording a real tx unrelated to MtGox as a deposit to a MtGox account. This would go unnoticed if the court take the deposit records as a fact without doing a proper audit/investigation following all BTC from deposit to withdrawal.