This sort of thing would never be possible with an iPad, because the Orwellian company would never give up enough control to developers to let this happen.  But this is what I imagine myself doing in court in 3 years or less:

Before trial, I load up all of my documentary and video evidence on a tablet.  I create a simple index to the documents with purpose-built software on the tablet.  When I open the index, I merely select the document I want, and it pops up on screen.  If I need to redact a specific portion of a document, I just draw over it, click a button, and a black box obscures whatever had to be redacted.

Once I get to the courtroom, I attach a wireless video output dongle onto the tablet.  This dongle enables me to display whatever is on my tablet through the projector in the courtroom.  At the bottom of the screen is a button that I push to blank the output, thus enabling me to sort through my evidence without it flashing up for the jury.

When an appropriate witness takes the stand, I hand him or her a slave tablet, and he or she is able to draw on the document, highlight appropriate areas, etc.  Whatever the witness does is saved as another version of the document, thus preserving everything.

During opening statement and closing argument, I can casually flip to the evidence I want to display, draw on it with my hand, and then set the tablet aside while I make whatever rhetorical flourish I’ve got in mind.

And now the best part.

Once the trial is over, my evidence and my opponent’s evidence is already on a half-a-dozen slave tablets that allow someone to do nothing more than view the documents.  We send those tablets back to the jury room, and the jurors have instant access to every piece of evidence from the trial.  If they want to have someone’s testimony repeated, the court reporter beams the appropriate portion of the transcript to the tablets.

With the right interface, and the ability to instantly blank the output while you find the right document, a tablet like this could absolutely increase the effectiveness of an advocate.  It could reduce the need to rely on trial technology experts, and it could revolutionize the way that lawyers, witnesses, and jurors interact with evidence.  Certainly, it beats lugging box after box of evidence to court and fishing for the right document to put under the document cam.

The best part is that this could be cost effective enough that any attorney who routinely tries cases could use this.  If I had some seed money, I’d build a business around selling these tablets ready-to-go.  Android tablets are going to be priced cheaply enough that a company could likely preload the software and sell the tablets for $700 bucks or so and still make a decent margin.  The consulting arm of the company would charge the hefty sums that other consultants do if lawyers wants us to preload the tablets with evidence and be available in the courtroom.

And the name for the device is already on the tip of your tongue: YellowPad.

If anyone wants to shoot me $100k to get the company off the ground, let me know. And if anyone wants to rip me off and start the business for themselves, just include me in the Beta and give me a finished YellowPad and I’ll be happy.