At the Main Menu, select Options. Select the Cheats option.

The following codes are possible and have the corresponding effect:

Code - Effect

Big Wheels - Wheels and Propelers double in sizeReoffender - Double the loss on all negative justice
Double Damage - Does Double the damage
Invincibility - Makes you invincible
Iron Man - Half health
Laser Law - All police weapons shoot blue lasers, others shoot red lasers
Law Lord - Gives full Justice at all times
Open Road - No civilian traffic
Speed - Increases character speed
Sticky Feet - You cant get thrown out of vehicles
Wild Water - Water is always choppy