The police accuse you of a crime, saying they have an eyewitness willing to testify they saw you at the scene of the crime. That does not mean a conviction is certain.
Eyewitnesses have helped convict many guilty parties. However, they have also helped convict many innocent people. Challenging their account is always possible.
Eyewitness accounts rely on human memory, which has flaws
Your memory is not as good as you think, nor is anyone else’s. There are several reasons for this:
Inattentional blindness: We do not see everything that is straight in front of us. We focus on certain things and miss others. It is a crucial survival skill, allowing us to concentrate on the rattlesnake about to strike or the mountain lion about to pounce. Pickpockets and magicians exploit inattentional blindness. They distract us with one thing, so we do not see something else they are doing.
A poor view: If a witness says they saw you, it is crucial to find out more about their position at the time. Were they close or far away? Did they have a clear line of sight, or did they glimpse the event across a street full of traffic? The time of day and the weather can also make a difference in the clarity of vision.
Persuasion: Children soon learn there are different ways to ask their parents for something they want. Asking in a certain way is more likely to produce the result they want. Police officers can encourage a witness to identify someone through how they ask questions. They may not even be aware they are doing it.
There is a long way to go from accusing someone of a crime to convicting them. False accusations happen all the time. If wrongly accused of a crime, you will need legal help to examine all aspects of the charge and build your defense.