SAN DIEGO — An investigating officer has recommended that the Marine at the center of the biggest prosecution of American troops in the Iraq war should not stand trial on murder charges, a defense attorney said yesterday.

Staff Sergeant Frank Wuterich, 27, of Meriden, Conn., is charged with the unpremeditated murder of 17 Iraqis in Haditha in 2005. The former squad leader allegedly directed his Marines in an assault that left 24 men, women, and children dead.

Lieutenant Colonel Paul Ware recommended that Sergeant Wuterich should be tried for the lesser offense of negligent homicide in the deaths of five children and two women, Sergeant Wuterich’s attorney, Neal Puckett, said.

Colonel Ware reviewed evidence against Sergeant Wuterich in a preliminary hearing known as an Article 32. His recommendation is nonbinding, and the final decision about whether Sergeant Wuterich should stand trial rests with Lieutenant General James Mattis, the commanding general overseeing the case.

If General Mattis accepts the recommendation for Sergeant Wuterich and a similar one for one of his corporals, which appears likely based on past practice, no one will face murder charges in the biggest case involving civilian deaths in Iraq.

“We’re both very pleased and also not surprised, given how the other cases have gone,” Mr. Puckett said. “There has never been any inkling that any of these Marines lost control or went on a rampage.”

Colonel Ware also recommended dropping charges of making a false official statement and telling a squadmate to do the same, Mr. Puckett said. If tried and convicted of murder, Sergeant Wuterich would face a maximum sentence of life in prison. Mr. Puckett said negligent homicide carries a maximum sentence of three years for each count.