Confessed to murder, can I be compelled to tell them where the body is?
If I confess to killing someone, in the United States, but refuse to tell them where the body is. Can I be compelled to tell them where it is so they can find evidence against me? Or can I exercise my right to remain silent and not help them prosecute me?
Assuming that I have no intention of testifying if they charge me. Assume I freely confessed to the the killing but implied that it was self-defense. Assume they are willing to charge me with murder, but find it hard without the body.
Can they use a subpeona or other mechanism to compel me to tell them or can I rest on my fifth amendment right to remain silent?
This is clearly nothing like a fingerprint, DNA, or handwriting. They don't want to identify me, they want to refute my self-defense implication with forensics.
For bonus points, what If I just found the body. I say I found the body. I'm the only one who knows where it is. They think I may have killed that person. Can they compel me to tell them where I found the body I claim I just stumbled on? Or can I rest on my fifth amendment right?
First, this is a hypothetical.
Second, contempt of court is very serious if there is no possible charge otherwise (for example, suppose if instead of a person, it's a company -- a company will follow a legal subpeona). Or consider a case where the person has a legal duty not to disclose the information unless compelled to.
Third, this could arise even if you don't confess. For example, you could mention that you found the body without realizing that it could result in charges against you. Later a lawyer could advise you not to tell them anything else.