The Amicus Brief is now posted. http://www.flcourts18.org/PDF/Press_Releases/Amicus_Brief_July_23_2013.pdf
It was filed by convicted sex offender Cleve Molette.
The cliff notes:
Molette is claiming that the jury did not receive instructions regarding the "Aggressor" statute, or considered whether Zimmerman committed a forcible felony against Martin, or initially provoked the use of force against himself. So, a new trial is required.
Frankly, this is a waste of paper. There is no evidence that Zimmerman initiated the use of force. There's no conclusive evidence against it (because the forensic investigation was botched), but circumstantial evidence points clearly to Martin. If he was indeed near his father's girlfriend's house as he reported to Jenteal, Martin would have had to circle back during that 4-minute gap to confront Zimmerman.
Furthermore, following a suspiciously-acting person at the behest of a police dispatcher isn't a "provocation".