[gamblor956]

he has no right to counsel so anything he said can be used against him

That's actually more a matter of the rules of evidence. Generally extrajudicial statements are considered inadmissible hearsay for trial purposes unless one of a number of exceptions applies. In this case, the statement against (self) interest exception would likely apply. (Other exceptions to hearsay might also apply.)

[drtillberg]

A party admission is non-hearsay in the US courts.[1]

[1] https://www.law.cornell.edu/rules/fre/rule_801

[gamblor956]

AKA the statement against self-interest exception...

I wasn't trying to give a lecture on the meaning of hearsay. But if you want to get didactic, the statement must be made by an opposing party and offered against them (i.e., is against their interests). A statement that is offered in support of an opposing party is, oddly enough, still hearsay. I have actually dealt with that issue in district court. This can happen in multi-party litigation, where you have cross-claims. For example, X, Y, and Z are parties to a lawsuit and have claims/counter-claims, cross-claims against each other. A statement by Y entered by X against Y would be admissible, but a statement by Y entered by Z could not be used in support of Y.