If someone runs a stop sign and hits you, you still need to prove that the other driver actually ran the stop sign. Your word may not be enough, especially if the other driver denies fault.
In every car accident case, the plaintiff must prove that, more likely than not, the defendant was negligent, and that the defendant's negligence played a part in causing the plaintiff's injury. So, if someone ran a stop sign and hit you, the first thing that you have to do is gather evidence. (Get the basics of fault in a car accident case.)
If there were any witnesses to your accident, make sure that you get their names and contact information. Liability in a car accident case can often be a matter of your word versus the other person's word, so witnesses can be critical.
If you were in a car accident, you may not be in a condition to gather evidence. But if you can, take pictures immediately. If you have a camera or a camera phone, take as many pictures of both cars and the accident scene as you can, from as many angles as you can. Walk down the street that the defendant came from and take pictures of the intersection, the stop sign, and any skid marks in the street. Take pictures of the debris from the cars, if there was any. If you were with anyone, take pictures of that person standing at the exact point of the collision.
If you do not have a camera or are not physically able to take any pictures after your injury, have a friend or relative take pictures of the intersection and of your car as soon as possible, and certainly before you get your car repaired. If you exchanged information with the defendant, and now have his/her address, you could also go around to the defendant's home and take pictures of his/her car. But make sure that you stay on public property while taking the pictures and do not trespass. Also, make sure to avoid any confrontation with the defendant or his/her family.
Many states have a law requiring the police to be informed if a car accident causes bodily injury or property damage that exceeds $500 or $1,000. Whatever the situation is, if you believe that the other driver ran a stop sign and hit you, you want to get it on record as soon as possible. Call the police, wait for them to arrive, and then tell them that the other driver ran a stop sign. The other driver might deny it, but at least you are now on record -- in the police report -- saying that the other driver ran the stop sign.
After you gather the evidence, now you and your lawyer can use the evidence to prove liability. If you got the names of witnesses who said that they saw the defendant run the stop sign, your lawyer will then contact the witnesses or have his/her investigator contact the witnesses. If the lawyer decides that the witness' information is helpful, the lawyer will generally take the witness's recorded statement. The testimony of a neutral, unbiased witness in a car accident case is key. Juries and insurance companies generally believe a neutral witness because that witness has no axe to grind in the lawsuit. If a witness says that the defendant ran a stop sign, that is often good enough to win your case, and if you've got more than one neutral witness saying the same thing, that's even better.
You and your lawyer can also use your photographs and physical evidence to try to prove liability. The damage that the collision caused to the cars is often good evidence to show how an accident happened, and who is at fault. For example, if someone runs a stop sign, that driver will often hit the other car broadside, and the damage to both cars will reflect that. In a stop sign accident, the negligent driver might also hit the innocent driver in the front or back corner. Either way, the negligent driver will usually have damage to his/her front in a stop sign accident, and the innocent driver will have damage to somewhere on his/her side.
Photographs of the accident scene can also show negligence. This is where a picture can be worth a thousand words. If, for example, there were no trees or obstructions in the area of the accident, the photographs will illustrate for the jury (or the insurance adjuster) how the defendant simply was not paying attention. The photographs will show that someone approaching the defendant's stop sign had a perfect view of the stop sign and of traffic on the cross street. In other words, the photographs will show that the defendant was negligent.