It doesn't change the facts though, I am right and the only way you can force somebody to testify is if they are ensured that they cannot be prosecuted because of a 5th Amendment... pesky thing that. In this case, since Impeachment doesn't punish past removal from office, and exclusion from eligibility to run for office, they could force him to testify in the impeachment trial if they removed any attachment and gave immunity from prosecution for the crimes they are accusing him of as Impeachment specifically does not attach to double jeopardy. Otherwise anything he said under oath could be used against him in a later criminal trial.
