Wallets are among the few personal items that officers are allowed to bring into the facility, the employee said, convenient for slipping a card into unnoticed. A wad of cash would be more conspicuous.
"That's the currency exchange throughout the jail with inmates," the employee said. "If you want to buy some weed, you get the money through the Green Dot."
Transferring money into jail or prison
Federal court filings describe how Green Dot cards are used by inmates at the Baltimore City Detention Center.
Step 1: A person outside buys a "MoneyPak" card, sold in denominations between $20 and $500.
Step 2: The card bears a unique 14-digit number, which the buyer sends to an inmate, often via contraband cellphone.
Step 3. The inmate can trade the code as currency within the facility or transfer it to a linked Green Dot debit card outside the jail or prison.
Sources: U.S. District Court, DEA