Final answer:
Before convicting a person of a crime that requires proof of mental fault, the government must prove beyond a reasonable doubt both the actus reus and mens rea of the crime. The high standard of proof in criminal law contrasts with the lower standard in civil cases and ensures a fair trial with constitutional protections.
Step-by-step explanation:
Before a person may be convicted of a crime that requires proof of mental fault, the government must prove, beyond a reasonable doubt, both the external physical act (actus reus) and the internal mental element (mens rea) of the crime. In criminal law, this standard of proof ensures that the jury has no reasonable doubt in their minds that the defendant committed the crime as accused.
The mental and physical elements of a crime are crucial, as they comprise the two necessary components for a conviction: the actual performance of the prohibited act and the intention or knowledge required to make the act a criminal violation.
Suspects must understand the charges and evidence against them, and be competent to stand trial. The constitutional protections including the due process of law ensure that an accused person is treated with fairness through every stage of the criminal proceedings. This reflects the high stakes involved in criminal trials, such as potential loss of liberty or life, as opposed to civil cases, where the standard of proof, 'beyond a preponderance of the evidence', is lower and typically involves the loss of property rather than liberty.