The writers of the Constitution were very concerned about people being forced to possibly incriminate themselves during a trial. Protecting a defendant from testifying against himself or herself requires that the prosecution must prove that the person is guilty of what he or she was charged. This is a very important concept and should be the principle followed in every case that goes to trial. The prosecution should have to prove a person’s guilt or innocence based on the facts of the case instead of forcing a defendant to answer questions that could be considered leading questions.
If the jury is impartial, it should make no difference if a person does or doesn’t testify. The jury should decide the case based on the facts presented during the trial. The jury should also follow the instructions given to them by the judge. If a jury factors into its decision whether a person did testify or didn’t testify, they would be allowing factors other than the facts presented in the case to help them reach a decision. This could lead to an incorrect verdict by the jury, which wouldn’t be something anybody would desire.