A former Navy diver was sentenced Wednesday to 12 years in military prison for involuntary manslaughter and assault in the 2009 death of his 14-month-old son.

Matthew McVeigh was also sentenced to a dishonorable discharge, a reduction in rank to the lowest level of E-1 and forfeiture of all pay and allowances.

McVeigh, 26, was on trial at Joint Base Pearl Harbor-Hickam on a charge of murdering Brayden McVeigh and would have faced a life term in prison if convicted.

But the miliary jury returned its verdict Tuesday after about nine hours of deliberations in finding McVeigh guilty of the lesser charge of involuntary manslaughter and assault, according to Navy officials.

The manslaughter charge carried a prison term of up to 15 years and the assault up to two years.

The same jury of seven junior officers also heard arguments on sentencing Wednesday morning and later started deliberating before reaching its 12-year sentence in the afternoon.

McVeigh will temporarily be held at the Ford Island brig pending transfer to a military prison on the mainland, Navy officials said.

"The Navy was committed to assuring a fair trial and that the interest of justice was paramount," spokeswoman Agnes Tauyan of Navy Region Hawaii said in a written statement.

"The Navy Ohana is saddened by the loss of Brayden McVeigh."

Under military law, McVeigh’s convictions are automatically appealed to the Navy Marine Corps Court of Criminal Appeals in Washington, D.C.

McVeigh was accused of striking Brayden on the head and shaking him at their Ford Island home.

The boy suffered massive hemorrhaging and a severely swollen brain, according to Navy prosecutors.

He was found unresponsive at the home on Sept. 18, 2009, and pronounced brain-dead two days later.

In the opening of the trial, prosecutor Lt. James Toohey told the jury that McVeigh was stressed and overworked on the job and at home, and was facing financial problems and his wife’s drug use.

McVeigh took out his problems on his young son in a pattern of escalating violence that included bruises, a broken arm and finally death, Toohey said.

Navy Cmdr. David Norkin, McVeigh’s attorney, suggested his client’s former wife, April, might have been responsible. Norkin told the jury that the prosecution wouldn’t be able to prove conclusively who killed the boy.

April McVeigh, who was not charged in the case, testified during the trial and denied killing her son or shaking him.

Matthew McVeigh did not take the witness stand.

He was a diver assigned to SEAL Delivery Vehicle Team 1 at Pearl Harbor at the time of his son’s death.