When a TAP Air Portugal flight from Accra to Sao Tome (the second leg of a continuing flight from Lisbon) was overbooked by three, the airline didn’t seek volunteers but instead selected 3 passengers at the gate to bump.
Usually passengers without seat assignments are at greatest risk of a bump, but two of the women had had their seats assigned for three months. Often the last passengers to check in might be at risk of being bumped, but they checked in early for the flight.