NORFOLK- The former commander at the U.S. base where Navy Seal Matthew McCabe is accused of assaulting an Iraqi detainee, testified today he issued guidelines just before the incident prohibiting prisoner abuse. He was the first witness in the trial of the 24 year old McCabe, the last of three Navy Seals to stand trial in connection with the arrest last September of Ahmed Hashim Abed. Abed is the accused mastermind of the murders of four U.S. contractors who were killed in Fallujah in 2004. Their bodies were burned, dragged through the streets and two of them were hung from a bridge.

The witness, who the court requested not be identified in the media, called his anti-abuse edict a “very important document,” but on cross examination said he wasn’t sure all his men had read it by the time the incident occurred.

The testimony came on a day in which a jury of 4 officers and 3 enlisted personnel was seated to hear the case, and opening arguments were also delivered. The prosecution claims McCabe is guilty of simple assault for striking a detainee in the midsection. McCabe and two other Navy Seals captured Abed and brought him to a U.S. detention center where the alleged abuse occurred. The other two SEALS have been acquitted.

In his opening argument, Defense Attorney Neal Puckett said, “Evidence will show the SEALs did something they are trained to do—go get someone and bring them back, essentially serving an arrest warrant.” As to the alleged assault, Puckett claims the detainee caused his own injury to discredit the Americans and that no abuse occurred.

Also on Tuesday, a two-and-a-half hour audio tape was played in which Abed describes the alleged assault. He said he was sitting in a chair when he was hit on the shoulder and the back, then fell to the floor. While down, Abed claims he was kicked in the stomach. He says he was blindfolded the whole time and can’t positively identify any particular assailant.

The defense is not happy with the translation of Abed’s testimony, but the judge said the transcript will be reviewed by another expert and that a new deposition is not necessary.

The trial is expected to last until the end of this week.

Fox News Channel’s Patrick Summers contributed to this report.