Left on passenger seat with windows down.

[S&W645]

+1. What if a teenager takes the keys to the second family car while mom and dad are gone somehwere, goes joy riding and kills someone. Are the parent responsible for leaving the keys in the basket by the door?

All depends on the state. However, in the case of a gun, it is a Federal law that you have to worry about. Some anti-gun DA could stretch the YHSA to say you provided a handgun to a juvenile by leaving it unsecured, if it had happened. Florida wrote into their laws that if a youth gets a gun as the result of a break in that they didn't cause, that the owner is not responsible for it. Example; Joe Convict breaks in steals you money and leaves door open. Sonny Jim, 16 years old, walks in thru the open door and finds a handgun on top of the dresser, grabs it and leaves. Owner is not liable because of Joe Convict's actions. Joe Cop breaking in also does not make the owner liable. At least the SCOTUS has seen fit to tell the states that the requirement to have the gun either locked up or disabled even when home violates the 2nd A.

 

[Fallschirmjäger]

" ... However, in the case of a gun, it is a Federal law that you have to worry about...."

Since you bring up the matter, what does Federal law have to say on the matter? Just a link will be fine, no need to copy and past.