There are cases where an individual unintentionally causes an incident. It's up to police to determine how and why the events took place, as well as the outside forces at work in creating the aftermath. Police should be mindful that even little details can affect crash reconstruction.
Police in Massachusetts are looking into a case where a tractor trailer hit a parked bucket truck with a worker in the outstretched arm. The force of the collision knocked the employee to the ground, but luckily nobody was killed in the incident. Accident reconstruction is still ongoing as police try to figure out why the truck driver lost control and struck the official vehicle.
In other cases though, law enforcement know the matter involves unintentional reckless driving. Canadian police are conducting crash reconstruction in relation to a collision that left one driver dead. A sedan struck the rear of a tow truck, killing the car's operator, but investigators believe the fault lies with the trucker who claimed he hadn't slept in more than a day. Whatever the reason, if extenuating circumstances are present, police need these details for crash diagramming.