During attract mode, draw either gun and press Start. You'll be given one life and allowed to play in a sample level for ten seconds. Shoot the enemies, and point the gun away from the screen to reload/shield yourself, as in the real game. You don't need any money to play this free sample, but you'll have to wait a few minutes before you can play it again.

This code MUST be done correctly and well-timed for it to work. First, insert your game's currency (preferably when you see the "Konami" splash screen), and during the title screen, press the trigger 12 times and hold the trigger the final time you press the trigger, press the start button while holding the trigger. You MUST ensure that you are doing the code on the "Lethal Enforcers 3" title screen in its entirety or the code WILL NOT WORK. After you press the start button, select either Dead Heat or Score Attack using the side button, select your name, and stage. If you see a police woman holding a Nanbu revolver and a shield as you start the stage, that means you did the code correctly and you'll play as the Police Woman throughout the game, although you'll still have access to munitions contingent to the stage's hero roles (i.e. if you were supposed to play as a Detective in Rival Heat and if you're a Police Woman, you'll still have access to a pump-action shotgun).

The trick here is to make sure you're inserting your game's currency at the Konami splash screen, doing the code on the title screen and timing the input right. Keep in mind that sometimes you won't see the title screen when you insert the proper amount of currency in the machine, so if you don't see the title screen, wait until you see the title screen and do the code. The timing is somewhat tricky so you'll have to practice to ensure the code works.