The OT doesn’t establish that Vader can “read minds”. It’s actually the opposite with Vader having to resort to torture to find out information others have.
So, my theory of what’s going on in the OT is supported by what we see in the OT movies.
It was established that Vader could read minds in ANH. The Mind probe is a Jedi ability to go through peoples minds in order to get useful information. That’s pretty much reading someone’s mind right there. Vader even said in ANH that “Her resistance to the mind probe is considerable” . And he wasn’t talking about the interrogator droid either. that ability was established in the OT. Just because he didn’t just read everyones mind doesn’t mean to say he couldn’t do it. We have seen Jedi have abilities then just don’t use them when they really could do with using them ( jedi speed run, super jump, mind control etc etc) .
Mind probe:
http://starwars.wikia.com/wiki/Mind_probe
I quote:
“Mind probes were used by IT-O Interrogation Units to extract information from captives. The Jedi were trained to resist mind probes.”
“Developed in secret by the Imperial Department of Military Research, IT-Os were used by the Galactic Empire to extract information from prisoners through the use of mind probes. Jedi, however, were known to have been trained to resist mind probes, requiring the use of other methods to procure information from them. One IT-O droid was used to interrogate Kanan Jarrus aboard Grand Moff Wilhuff Tarkin’s Star Destroyer Sovereign. However, torture was eventually handed over to The Grand Inquisitor. Another IT-O was used aboard the Death Star to extract information from Princess Leia Organa, although she proved to have considerable resistance to the mind probe. The IT-O was later deployed on Yavin 4 during the Empire’s cleanup operations at the former Alliance base.”
I thought this was common knowledge ever since 1977, I guess I was wrong. Vader did not read or attempt to read Leia’s mind.