OAKLAND (BCN) -- A prosecutor and a defense attorney differed Monday over whether an Oakland man deliberately murdered his 3-month-old son nearly four years ago or caused the boy's death by dropping him in an unfortunate accident.

Prosecutor Tim Wellman told jurors in his opening statement that the trial of Fernando Loughlin, 36, is simple and is "a case about a man who murdered his own child," Julian Loughlin, who died on March 8, 2007.

Wellman said Loughlin, who worked as a business consultant, "was responsible for caring, nurturing and protecting his child, but instead he killed his child."

But Loughlin's lawyer, William Locke, said Julian died because Loughlin was bathing him and accidentally dropped him when he got distracted by his other boy, who was 20 months old at the time.

Locke said the question in the trial is "whether the prosecution can prove beyond a reasonable doubt that Mr. Loughlin inflicted horrible and unimaginable injuries on his 3-month-old son."

Locke said he believes it would have been out of his character for Loughlin to deliberately kill his son because he has no history of violence or abuse toward children.

The defense lawyer said the case will involve competing medical interpretations of what caused the injuries that led to Julian's death, and he said he believes there is no medical evidence to prove the prosecution's theory that Loughlin intentionally killed Julian.

"We need to accept the limitations of science. There are some questions it can't answer," Locke told jurors.

He said Loughlin should be found not guilty of murder as well as a second charge of assault on a child under the age of 8 causing death.

Wellman said Loughlin and his girlfriend were raising their two young sons at an upstairs two-bedroom apartment on Kempton Avenue in Oakland.

The prosecutor said Loughlin was alone with the boys on the morning of March 3, 2007, because his girlfriend went to a class.

Wellman said that shortly after 11 a.m. that day, Loughlin called 911 and told a dispatcher, "I have a 3-month-old who's unresponsive and not breathing."

Julian was rushed to Children's Hospital in Oakland but died five days later.

Wellman alleged that Loughlin's later claim that he accidentally dropped Julian is suspicious because he told authorities "many lies" about what happened.

He initially said that Julian had been sleeping, and that when he checked on his son, he noticed that he wasn't breathing, Wellman said.

Wellman said when Loughlin called 911, "He acted like he had no idea what was happening."

But he believes that Julian was dying was "because of the abuse inflicted by the defendant" (Loughlin).

However, Wellman admitted that there aren't any eyewitnesses who can help him prove his theory that Loughlin deliberately killed his son.

"What happened behind closed doors is the subject of this trial," he said.

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