When a traffic wreck occurs, people are sometimes tempted to lie about what happened in order to avoid the potential financial or criminal consequences of being found at fault for the accident. Frustrating though it may be, there isn't much you can do to stop another party from lying about what happened. Try not to worry about it. After the accident, their actions are largely irrelevant. Focus your energy on building up your own case, not tearing down theirs. That's the best way to protect your interests.
Document the Accident
If you are involved in an accident, don't just exchange insurance and driver's license information with the other party. Collect evidence of what really happened. If there were bystanders who witnessed the wreck, ask them if they would be willing to make a statement to the police, and then get their contact information. If you have a camera, use it to take pictures of any damage or other points of interest at the scene. Observe the people from the other vehicle for evidence of intoxication and make a note of whatever you find.
File a Police Report
The most important thing you can do to protect yourself from fraud is to file a police report detailing your side of the story. This report will be the decisive source of information for the insurance companies and, if necessary, the courts. Tell the police exactly what happened. Let them know of any bystanders who might be willing to talk to them, and inform them of any notes you took or evidence you collected. Be sure to mention who you think is at fault for the wreck. If you don't have a good idea of who is at fault, then tell the police that you do not think you are at fault, but don't go so far as to accuse the other party. These statements are your best protection against fraudulent claims.
Contact Your Insurance Company
After filing the police report, contact your insurance company and tell them everything you told the police. Your insurance company is initially going to be on your side. They won't want to have to pay any money, and they'll exert a reasonable effort to protect their bottom line.
The other party may resist your claim, and, if he or she lies in the process, this is your opportunity to dispute these lies explicitly. If you have any physical or logical evidence to discredit them, pass it along to your insurance company.
If your insurer offers you an unsatisfactory resolution---especially if the resolution involves an admission of liability on your part if you feel the accident was not your fault---then instruct them to take your claim to mediation. If mediation is resolved in your favour, that's the end of the story. If not, then you may want to escalate the claim by hiring an attorney and taking the case to arbitration.
Report Suspected Fraud
Some people intentionally stage auto wrecks in order to make false insurance claims. This is insurance fraud, an illegal industry that pilfers billions of dollars annually. If you are involved in an accident and suspect that the other party is a professional con artist who staged the wreck deliberately, inform both the police and your insurer of your suspicions---and be prepared to hire an attorney.