The most important part of a jury trial happens long before the actual trial date.
It is very important that necessary depositions are conducted, with the transcript reviewed in intimate detail enough time before the hearing to file those pages as Exhibits that can be used for impeachment purposes.
Additionally, in Wisconsin, they can be used as substantive evidence. What does it mean that they can be used as substantive evidence? Well, it means that witnesses can confirm they previously testified a certain way if their testimony at trial is less helpful in some way. For example, in a certain jury trial in which I was Plaintiff's counsel, the witness had used very colorful language to describe the setup at the hands of Plaintiff in a deposition. However, during trial, he was more reserved. I struggled to consider how to best get the colorful language in front of a jury. Since I had already submitted the Exhibit to the court - as pre-marked - I was permitted to ask the witness if he had testified in the way I wanted to introduce previously, and then to read in what he had say. Even though it wasn't "inconsistent", I was able to put it in front of the jury. That colorful language was something that elicited a reaction from the jury. Then, knowing the effect it had, I was able to use that part of the transcript in closing argument as part of my theme.
So, how did I get there in the first place? Well, the place that started my ability to use the deposition transcript was nearly one year earlier, with proper preparation for the deposition at a time when the witness was less nervous or reserved. It is possible that one will wish to first conduct discovery OR - depending on how honest the witness is perceived as being - it may be better to "catch" the witness off guard at the deposition with certain questions he or she would see/hear for the first time.
By the time of the deposition, the attorneys have already considered what witnesses might be helpful either to prove an element in the case OR to help support or undercut the credibility of one of the parties on a fact for which there's an implied or explicit claim of fabrication. Remember, the jury will be listening for evidence at trial in the form of believable witness testimony, so who will be helpful at deposition can take many forms.
With well used depositions, either to support or undercut a witness' credibility, before a jury, the evidence in the transcript can be as helpful as physical "proof" - what most people consider evidence before they sit in a jury box.