If person on a motorcycle forgot to turn on his headlight and?
There are far too many variables involved in such a case to say definitively what the liability might be. In a criminal matter, the distracted driving of the phone user is probably sufficient to be the proximate cause of the motorcycle riders injuries and could be prosecuted for vehicular assault or some other felony crime, though its equally likely that both would be cited for their individual traffic infractions. In a civil matter, its going to depend largely on whether or not the jurisdiction in which this accident occurs allows for comparative negligence, as well as what evidence there is for each of the posited facts, and how much the jury or judge believes that evidence. In a comparative negligence state, the jury would weigh the negligence of both parties and determine how much liability each has for the accident, splitting or reducing any judgment that is issued based on the % of negligence owned by the person who was negligent. In a state without comparative negligence, the person who took the last action that led to the accident would likely be liable, as that action is the proximate cause of the injury. In this case, that would be the person dialing a number on their phone as being a distracted driver is illegal in nearly every state, whether or not they have adopted specific laws related to the use of phones while driving. A good way to look at it is, had the person not been using their phone, its likely that the accident would not have happened and the motorcycle rider not been injured. Now, there are a thousand tiny facts that could change the situation such as: did the motorcycle rider cross the center line? Any little fact in addition to those posed could alter the outcome significantly. If this relates to a real-world scenario, you should absolutely obtain a consultation with a local personal injury attorney, who can review all the facts of the situation and compare them to the applicable law in your jurisdiction to provide you with actionable advice.