In the first two cases you list below there are big problems with your comparison. I don't know enough about the third case to have an opinon on that one. Michael Walker was only a minor player in the spy ring and got a reduced setence for turning evidence against his father (who was the leader and got multiple life sentences).

Second, from what I have read the whole Richard Miller case was messed up, and the government had difficulty showing that he was actually guilty of espionage. He had classified documents at his apartment and was having an affair with a woman who was a foreign spy, both grounds for dismissal but neither a major crime on their own.

As for Pollard, I'm sorta split on his case. Superficially it looks like he got a bit of a raw deal, but it has also never been made public exactly what information he passed to Israel except that there was apparently a lot. He also greatly hurt his case by working a plea deal with the government and then violating the deal before the trial was even over.

From what I have read, the Israeli government has not helped his case either. Their repeated public support of Pollard with a "Yes he was a spy but he was good one" line doesn't help him here. And they have apparently often use his cases as a negotiating ploy, with no real interest in getting him released.

Jay