From Jeff Richardson at iPhone J.D., "Using an iPad to recreate a scene in a deposition"--
A picture can be worth a thousand words. A picture that you use with a witness to exactly identify where he says something took place can be much more valuable than that when you later want to impeach the witness at trial, showing that the events could not possibly have unfolded as he previously testified. Thanks to the iPad, you have the tools to create a photograph with markings right there in the deposition, which may end up being the reason that you win your case.
Read the full post for a step-by-step method of using and marking maps and locations using an iPad during a deposition.