Can a police officer write a ticket for an accident that they did not witness, especially when the other driver was at fault?

When a police officer writes a traffic ticket, it has the same legal effect as when someone is charged with a crime - it is an accusation, not a conviction. Most times, when a police officer responds to a collision, the officer is usually not an eyewitness to the event. Instead, the officer typically collects information, including verbal statements, from people involved in the collision. In some cases, police officers either do not take, or cannot obtain statements from all parties involved. this sometimes leads to tickets and charges made based on less than full information. It is for this reason that no one is convicted of a traffic violation without having the opportunity to contest the charges in court. It sounds like the officer involved in this case took the word of the motorcycle driver, and did not investigate the information your niece had to offer. It is entirely possible the officer never heard anything about any other vehicle other than her car. The good news is that your niece still has the ability to contest the charge and set the record straight.

The answer to your question is yes. In fact, policy officer often write citations for accidents they did not see based on statements taken at the scene. I would consult with a local traffic ticket attorney to help you with your neice's citation.