SAN DIEGO -- Fractures began appearing Tuesday in the defense of three U.S. Coast Guard crew members charged in the boat crash death of an 8-year-old boy on San Diego Bay last year.

During a preliminary hearing in Alameda, lawyers for Petty Officer 3rd Class Paul Ramos, the pilot of the 33-foot patrol vessel at the time of the fatal accident, argued that their client should be tried separately because the defense claims of his two colleagues have been "antagonistic" to him.

Ramos faces an allegation of involuntary manslaughter in the death of third-grader Anthony DeWeese of Rancho Penasquitos. Charged with negligent homicide are Petty Officer 2nd Class Ian Howell, USCG Station San Diego officer of the day, and boat crewman Petty Officer 3rd Class Brittany Rasmussen.

A fourth boat crewman, Petty Officer 3rd Class Lavelle Teague, faces lesser charges in separate proceedings.

Anthony was killed and several members of his family's boating party were badly hurt Dec. 20 when the Coast Guard boat slammed into the back of their recreational vessel during the annual holiday Parade of Lights on San Diego Harbor.

The youngster was rushed to UCSD Medical Center, where he was pronounced dead a short time later. A 4-year-old boy who had been sitting next to Anthony on the 24-foot pleasure boat, called the Sea Ray, suffered a fractured skull.

Authorities said the Coast Guard boat was responding to an emergency report of a grounded vessel when the collision occurred. A lawyer for the DeWeese family, however, has asserted that the crew had been traversing the bay at excessive speeds earlier in the night.

Lawyers for the defendants argued that all legal proceedings in the case should be held in the city where the accident occurred because they can't put on a fair defense so far away from the witnesses involved.

The preliminary hearing, known as an Article 32 in military parlance, is being held at the San Francisco Bay Area headquarters of Coast Guard District 11, which includes San Diego.

At least 20 people will be called in during the proceeding, including the deceased boy's father, Alan DeWeese, but not his mother, Caroline, who was seated in the courtroom looking stoic.

Coast Guard officials have said it may be the first time in modern history that any member of the federal maritime agency has been charged with manslaughter for actions taken in the course of duty.

Following the preliminary hearing, Rear Adm. Joseph Castillo, who brought the charges, will decide how the case will proceed.