It could mean that they're looking for a key piece of information and nobody on the jury can accurately recall what he said and how he said it.
It could mean that they're bored and want to extend the time they spend on jury duty.
The reality is that it could mean anything.
The problem is that we, as attorneys, don't know the motivation for the jury requesting a readback of key testimony.
But there's a difference here. In this example, the jury has requested that ALL of this witness' testimony be read back. That's different than having a small part of testimony read back.
At the end of the trial, after the judge has given the jury instructions on the law, the judge will tell the jury that if they want, they can have testimony read back to help them in their deliberations. Remember, there is a court stenographer in court every day to record everything that is said during the trial.
There have been some instances where jurors have asked the judge to have a witness' entire testimony read back. Often the judge and the attorneys will be shocked when this happens. The first reaction is, "Did they not hear the testimony the first time?"
"His testimony, both direct examination and cross examination took an entire day! Are we going to spend an entire day just reading back his testimony?"
In that case, the judge is likely to refuse the jurors' request to re-read all his testimony. Instead, he will tell the jury to focus on a specific part of his testimony that they are having trouble with. The court, along with the attorneys, can then identify that section of testimony dealing with that issue and have that segment read back.
When the jury requests all of the witness' testimony read back, we wonder what they were doing when the witness was testifying. Were they asleep? Did they wander off? Were they not paying attention? What could prompt them to want ALL of his testimony replayed?
It could be on juror wants to make sure what he said. Maybe one juror didn't understand the testimony. Who knows?
Even in cases that go on for many weeks or months, the judge will likely not allow a witness' testimony to be read back in its' entirety. That would take up a tremendous amount of time and not really help the jury. Rather, he'll ask the jury to refine their request and limit it solely to the issue they're having with this witness.
That will often solve the problem.