Why can a criminal defendant choose not to testify in an Anglo-American trial?

In Anglo-American trial practice, a criminal defendant may choose not to testify because they possess the privilege of refusing to be called or sworn as a witness. This right is rooted in the principle against self-incrimination, which protects individuals from being compelled to provide evidence that could expose them to criminal punishment.123

In the United States, this protection is enshrined in the Fifth Amendment, which states that no person shall be compelled in any criminal case to be a witness against themselves. This safeguard is fundamental to the judicial system, which presumes the defendant is innocent and places the burden of proof on the state. Because words can be used powerfully against an accused person, the law ensures that defendants are not forced to provide testimony that could be manipulated or used to secure their own conviction.3

While a defendant may exercise this privilege with considerable latitude, they must be aware that if they choose to step into the witness box and testify, they waive this privilege and may be interrogated as an ordinary witness.1