A more thorough explanation:

Definition: Cumulative error is the prejudicial effect of two or more trial errors that may have been harmless individually. This means that even though each error on its own may not have affected the outcome of the case, when combined, they can lead to a wrongful verdict.

Example: Let's say a defendant is on trial for robbery. During the trial, the prosecutor makes several improper statements that the defense attorney objects to, but the judge overrules the objections. Additionally, the judge allows a witness to testify about something they didn't actually witness. Individually, each of these errors may not have been enough to change the outcome of the trial. However, when combined, they could have influenced the jury's decision and led to a wrongful conviction. This is an example of cumulative error.