Note: This game is also titled Gyakuten Saiban: Yomigaeru Gyakuten.
During the Case 5 ending credits on the touch screen, fingerprint powder will be applied and blown away to reveal the credits. Eventually, a dialogue scene with a character will appear. Tap the touch screen at this time as though applying fingerprint powder to it and blow it off (as done during the game) and a hidden drawing of that character will appear on the top screen.
Have the Game Boy Advance game Gyakuten Saiban in the cartridge slot.