There would be little justification and benefit to law enforcement to file a SAR on 1 cash deposit of $5,000. You need to look into what you know about the customer, such as occupation, account history, what other activity in and out of the account is happening, etc to determine if the activity is suspicious. You might want to begin to monitor the activity more closely for a while to see if more cash is deposited or where the $$ is going. If all else fails, strike up a conversation with the customer next time you see him and try to find out more about the source of the cash.