Question

Why doesn't the government get to punish anyone it suspects of a crime in any way it wants? Why does it generally have to prove guilt?

Answer 1

Because our judicial system is set up on the idea of an adversarial system.

Explanation:

Our trial system is based on the 6th Amendment which in itself answers your question: The 6th Amendment contains five principles that affect the rights of a defendant in a criminal prosecution: the right to a speedy and public trial, the right to be tried by an impartial jury, the right to be informed of the charges, the right to confront and call witnesses, and the right to an attorney.

Additionally, the burden of proof, that a crime has been committed, always lies with the state. That is, the state has to provide reasonable proof that the defendant is guilty of the charge. Conversely, the defense has an equal opportunity to prove its client's innocence.