Positional asphyxia is a death that occurs when a subject's body position interferes with breathing. This training bulletin informs Chicago Police Department members of potentially dangerous restraint positions that must be avoided during custodial arrest and transportation. Positional asphyxia can occur when a subject's chest is restricted from expanding properly or the position of the subject's head obstructs the airway. Officers should never: restrain a subject's hands and legs together; leave a subject in control restraints lying on his back or stomach; put weight on the subject's back for a prolonged period; or keep a subject waiting for transportation in a restrained position without proper monitoring. The risk of positional asphyxia increases in the presence of alcohol intoxication, drugs, physical ailments, delirium, or respiratory diseases. When feasible, officers should handcuff an arrestee with both hands behind his back, palms outward. Although most officers have no reason to expect death to result from restraining a subject, it can happen. The bulletin claims that exercising caution and common sense can lessen the potential for in-custody deaths from positional asphyxia.