Rule 1221 Evidence of a statement offered against a party is not made inadmissible by the hearsay rule if the statement is one of which the party, with knowledg…

When someone agrees with a statement, either by saying so or by acting like it is true, that statement can be used against them in court.

For example, if someone hears another person say "we planned this together" and they nod, smile, or say "that's right," their reaction can be treated as if they said it themselves. The court sees their agreement as making the statement their own.

This rule also covers silent agreement. If a person hears something said about them and does not deny it when a normal person would, that silence can count as accepting the statement as true. The key is that the person knew what was being said and chose to go along with it.