Why are subpeonas justified but not compulsory juries?

In your May 15th podcast, you contrasted your position on jury duty with that of Dr. Peikoff's, saying that jury duty constituted the initiation of force. My understanding is that Ayn Rand's position was that subpoenas and the jury selection process was entirely consistent with justice (Peikoff mentions it here: http://www.peikoff.com/2010/06/07/ayn-rand-accepts-the-right-of-the-state-in-the-administration-of-justice-to-subpoena-witnesses-but-this-depends-on-the-use-of-force-and-coercion-of-witnesses-to-testify-why-is-this-justified/). Juries are selected using subpoenas. How would you reconcile being for subpoenas but against jury duty? And, does this also mean that you disagree with Ayn Rand's view of justice?