Learning that Princess Leia lied about the location of the rebels on Dantooine from officer Cass (played by Patrick Jordan, voice dubbed by a US actor), the angry Tarkin orders her execution, but his scene with Vader in the conference room had some longer deleted dialogue- look carefully and you can see that Dave Prowse is clearly talking and gesticulating a point to Tarkin after James Earl Jones post production dialogue has finished, as seen in the above image.
Lines in yellow indicate the filmed but deleted dialogue.
This scene was ultimately split in two with the film's final editing, after Tarkin's "terminate her" line.
INT. DEATH STAR- CONFERENCE ROOM
Imperial officer Cass stands before Governor Tarkin and the evil Dark Lord Darth Vader.
OFFICER CASS: The scout ships have reached Dantooine. They have found the remains of a rebel base... but they estimate it has been deserted for sometimes. They are conducting an extensive search of the surrounding systems.
TARKIN: She lied! She lied to us!
VADER: I told you she would never consciously betray the rebellion... unless she thought she could destroy this station in the process.
TARKIN: Terminate her immediately!
VADER: And lose your only link to the rebel base? She can still be of value to us.
TARKIN: You'll get nothing more out of her. I'll find that hidden fortress if I have to destroy ever star system in this sector.
A quiet beeping tone interrupts the governor.
TARKIN: Yes (this line was added in filming)
VOICE: We've captured a freighter entering the Alderaan system. It's markings match those of the ship that blasted its way out of Mos Eisley.
VADER: They must have been trying to return the stolen data tapes to the princess... we might be of some help.
Vader's last line was changed in post to, "They must be trying to return the stolen plans to the princess. She may yet be of some use to us".