So how would paying money into someone's account by mistake,
qualify for a criminal complaint?
Basically if you deposit the money into the wrong account, sometimes you dont realise for quite some time. By which time the money would have been spent. In such cases, you don't really have a criminal complaint, because the person may not have known that the money was not for their benefit. In such a case, you have a claim for unjustified enrichment, which is a civil matter.
However, the theory at least is, if you find out before the money is spent, you can tell the bank to advise their client that the money was paid over in error and is not for their benefit. If they then spend the money that was not intended for them, then technically speaking they are committing an act of theft.
I am however not so sure about this. In law there is a principle called co-mingling, cant remember the latin terms. The principle however is that you have something like olive oil ( a real example), if I steal your olive oil and place it in a container which now contains only your olive oil, then you can identify your oil and have a claim for the return of THAT oil. However, if I take your oil and mix it with mine, your oil mixes with mine and becomes MINE! You then only have a damages claim to the value of the oil in question.
Same can be said for money. If I take your coins and throw it into my piggy bank with my coins, an we break it open, unless you can identify YOUR specific coins, your coins become mine and all you have is a claim for unjustified enrichment.
So, if by mistake you deposit money into my bank account with money already in it, then that money becomes MINE and you have a damages claim against me, irrespective of whether or not I know that the deposit was in error. So if the money technically becomes mine, how then can it be stealing? Yes you have a claim against me, but me spending money that has mixed with my own cant be stealing.
Arguably speaking if money is deposited into an empty bank account, then you will have a claim for those specific funds!?!?!