A more thorough explanation:

Rational doubt, also known as reasonable doubt, is the belief that there is a real possibility that a defendant is not guilty. It is the doubt that prevents one from being firmly convinced of a defendant's guilt.

In a criminal trial, the standard used by a jury to determine whether a defendant is guilty is "beyond a reasonable doubt." This means that the jury must begin with the presumption that the defendant is innocent and only find them guilty if they are convinced beyond a reasonable doubt.

For example, if a person is accused of stealing a car, the jury must consider all the evidence presented in court and decide whether they are convinced beyond a reasonable doubt that the person committed the crime. If there is any doubt in their minds, they must find the person not guilty.

Rational doubt is not a mere possible doubt, but a doubt that remains even after the entire comparison and consideration of all the evidence. It is a doubt that leaves the minds of jurors in a state where they cannot say they feel an abiding conviction, to a moral certainty, of the truth of the charge.

Overall, rational doubt is an essential part of the criminal justice system as it ensures that innocent people are not wrongly convicted.