It's a medical malpractice trial.
The defense attorney has hired a medical expert to come in and defend their claim that the doctor who is being sued nothing wrong. In order to reach that opinion, the medical expert needed to review the injured victim's medical records.
The attorney sent the defense expert most of the medical records and the legal pleadings in the case.
At the beginning of cross examination, the attorney representing the injured victim will often ask the defense doctor exactly which records he was given to review.
If it turns out that the doctor did not receive all the patient's medical records, that now opens the door for significant cross examination.
The reason is that if the doctor has not reviewed certain medical records, then his opinions and conclusions may be incomplete or inaccurate.
It gives the attorney who is cross-examining this expert the opportunity to show to the jury that if certain records had been reviewed, the information contained in them would be significant enough to alter the doctor's opinion about what was done correctly and what was done incorrectly.