Reasons for the child being left in the car:
(1) A child playing in an unlocked car.
(2) The driver forgets or is unaware that the child is in the car.
(3) The driver knows that the child is in the car AND wants to run a quick errand.
(4) The driver knows that the child is in the car AND does not want to be bothered by the child (to get a drink, go gamble, etc).
Reasons that the driver may forget about a child being in the car:
(1) the child is asleep
(2) the person assumes that the child is with another parent
(3) there was some change in the person's routine
(4) the person is not thinking sharply (hangover, medication, stress, etc)
Risk factors associated with a susceptibility to hyperthermia:
(1) small infant
(2) high heat and humidity
(3) comorbid condition (heart disease, metabolic disorder, etc)