That's the advice offered by Ben Riley in his article "Use of Demonstrative Evidence at Trial"--
We suggest using your law firm’s own resources . . . to produce computer graphics in-house. Not only will it cost much less than using an outside vendor, the results will be better because of the trial lawyer’s central role in the development process. And with the myriad of sophisticated software publishing programs now on the market, you can achieve amazing results in-house.
Though the 1997 article is slightly out of date, it contains a number of tips that will be useful to you if you want to try creating your own computer-generated charts, graphs and animations.