( CNN ) -- The defense team for George Zimmerman -- charged with murder in 17-year-old Trayvon Martin 's death -- continued their offensive Friday , pressing in court for access to information they hope will shed light on what happened and exonerate the Florida man . In an interview Thursday with `` InSession 's '' Jean Casarez , Zimmerman 's lawyer Mark O'Mara previewed the court action and reiterated the position that Martin , and not his client , was the aggressor in the February 26 incident . `` We will have a ... trial , and if that trial is fair , he 's going to be acquitted , '' O'Mara said , ruling out a deal in which his client pleads guilty to lesser charges . While driving through his Sanford , Florida , neighborhood that winter night , Zimmerman spotted Trayvon Martin , whom he described on a 911 call as `` suspicious . '' A dispatcher told the 28-year-old neighborhood watch volunteer not to follow Martin , but he did anyway . After an altercation , the unarmed African-American teenager was shot dead . Weeks after the incident , the case drew national media attention , and activists demanded an arrest . On April 11 , Zimmerman was charged with second-degree murder . Defense lawyers have steadfastly maintained their client 's innocence , saying Zimmerman was badly beaten and acted in self-defense . They have challenged key pieces of the prosecution 's case . One of the most potentially pivotal pieces deals with a 911 call from that night in which someone can be heard screaming for help . The thinking is that the person pleading for assistance -- whether it was Martin or Zimmerman -- was on the defensive , and the other was the aggressor . A defense motion filed Monday in Seminole County court , which the prosecution replied to Friday , asks that Zimmerman 's lawyers be allowed to question for a second time Sanford police investigator William Erwin . Zimmerman 's lawyers claim that Erwin overheard the late teen 's father say the screaming voice was not that of his son . The father , Tracy Martin , has said he is `` positive '' the pleading voice is that of Trayvon . In a response Friday , Assistant State 's Attorney Bernardo de la Rionda criticized the defense 's arguments and said Erwin `` never mentioned anything about overhearing Tracy Martin talk about the voice . '' But the lead prosecutor did n't object to O'Mara and other lawyers deposing Erwin . Additionally , Zimmerman 's defense team filed several new documents Friday . One asks that the prosecution `` disclose all witnesses known to the state who claim to be familiar with Trayvon Martin 's or George Zimmerman 's voice that have heard '' the 911 call . Zimmerman sues NBC Universal over edited 911 call . Another motion asks the court to force Benjamin Crump , the Martin family 's attorney , to turn over the original recording and recording device that he used to first interview the late teenager 's girlfriend . Asserting that the young woman can prove Martin was killed `` in cold blood , '' Crump said in March that the girlfriend `` completely blows Zimmerman 's absurd self-defense claim out of the water . '' But defense lawyer Don West said Thursday that the recordings he 's aware of are a `` copy of a copy that 's disjointed and chopped and obvious that it was edited . '' On Friday , Crump said he has already turned over the tape . `` The phone records speak for themselves , '' the lawyer said . `` She tells him to run . He runs . And then , when you go through the 911 tape , George Zimmerman admits that he is pursuing Trayvon . '' Zimmerman filed a different motion Friday , asking that he be allowed to remove his GPS monitor and leave Seminole County without the court 's permission . The document alleges that Zimmerman and his wife have lived `` in fear of violence at the hands of those who would wish ( him ) harm based on their misinterpretation of the events . '' These and other court filings Friday follow other moves by Zimmerman 's team in recent days to raise questions in court and in public about the prosecution 's case . The next hearing in the case is set for December 11 . Last week , they released a photo of a bloodied Zimmerman taken a few minutes after Martin was shot dead . On Thursday , they filed a lawsuit against NBC for a report that O'Mara claims portrays his client as a racist and murderer ; the lawyer called it `` one shining example of what was done wrong to George . '' `` They took an event and made it highly inflammatory , '' said O'Mara of the NBC report that , according to the lawsuit , selectively edits audio of Zimmerman 's 911 call to make him sound racist . `` They wanted to be first , and ... they wanted to have the most sensational headline of that day . And they just did it . They just presumed , I think , ... they had a racist . '' Zimmerman , who is Hispanic , is accused of fatally shooting Martin , who was African-American . NBC Universal disputed the accusations and issued a statement saying : `` There was no intent to portray Mr. Zimmerman unfairly . We intend to vigorously defend our position in court . '' CNN 's George Howell and Jason Hanna contributed to this report .
Trayvon Martin is charged with murder in the death of George Zimmerman , April 11 . His lawyers want to loosen restrictions on Zimmerman , saying he lives in fear . The defense asks to talk to an investigator about a pleading voice on a One tape . Martin says Zimmerman killed the unarmed Martin in self-defense .