If a person accepts a presidential pardon, can they be forced to talk about the crimes they were pardoned of?

Question

This question stems from Can a person refuse a presidential pardon?

There are also other practical effects to accepting pardons, such as waiving of fifth amendment rights relating to the pardoned crimes, since it would be impossible to self incriminate anymore. (...)

And I went into the comments for clarification, but things got big enough to deserve its own Q&A.

If you get asked a question under oath which would force you to admit to a crime if answered truthfully, i.e you would incriminate yourself as to having commited a crime, then you can choose not to answer by "pleading the fifth" e.g. invoking the fifth amendment's protection against self incrimination. Most western nations have this right. If you get pardoned for a crime, it's essentially not a crime anymore, so you can't rely on fifth amendment protections to allow you to opt out of being asked about the details. – Magisch

Now the scenario, John Doe was accused of [crime], prosecuted and condemned to a death sentence by a jury of his peers, etc. Then was offered a presidential pardon and he accepted.

Interested parties can question him (where are the bodies, how did you enter the CIA database, what is the passcode to your smartphone we didn't return). Can he be forced to answer?

Answer 1

The legal theory behind forced testimony due to immunity/pardons hasn't really ever been challenged, it is theoretically allowed according to this answer. In either case compelled testimony isn't very helpful in most situations. Such testimony wouldn't help in other court cases, the fact it was forced could possibly even keep that evidence from being used against others. Oliver North's immunized testimony is a good example, the mere existence of it prevent any convictions related to his actions in the Iran Contra affair from being upheld. The other problem with the theory is scope, just because someone can no longer be prosecuted for crime A, forced testimony about A may reveal crimes B, C, and D which a person still definitely has a right to not self incriminate themselves.

The concept of being able to nullify the fifth amendment is also the cornerstone in most proposals to legalize torture. This is important because at some point any means of compelling testimony is arguably torture. This concept hasn't been used because it's a really slippery slope. Forcing testimony from an unwilling person is difficult, holding a person until they answer is effectively indefinite detention. Furthermore, they would be detained in relation to a crime that they are immune from, which would make for a good human/civil rights case. There is a very real danger that attempting to compel testimony could backfire spectacularly, so it's likely this will remain theoretical in nature.