In personal injury law, the act that begins a natural and continuous sequence of events ultimately producing the injury is called the proximate cause.  Had this initial act not happened, no injury would have occurred. Liability for an injury falls on the last negligent act that produces the injury. For example, if you roll a ball down a hill and it is picked up by a random passerby, who throws it through a window, which breaks and injures other people, you are not responsible, as your action is not the proximate cause of the injury; the act of the passerby is the proximate cause.