The California man who allegedly killed his girlfriend with a homemade cannon had previously served prison time on weapons and auto theft charges and had pleaded guilty to domestic violence against the woman.

His history with the law could be why Richard Dale Fox is facing a first-degree murder charge, even though San Diego County Deputy District Attorney C.J. Mody has said there was no evidence the killing was intentional.

Fox, 39, pleaded not guilty Thursday in the death of Jeanette Ogara, 38. Ogara died instantly when shrapnel from the device went through the couple's trailer in Potrero, San Diego County, and struck her early Tuesday morning.

In a tearful 911 call he made to police after the device detonated, Fox can be heard sobbing and hysterically describing what happened, saying it was an accident.  In a jailhouse interview following his arrest, Fox - who sustained shrapnel  injuries to his right  leg - said he was sorry and wished he had been the one who caught the blast, rather than Ogara.

"(Fox's) emotion won't make or break the charge, but the fact that the prosecutor is saying we don't think this is intentional makes you wonder well then, why did they feel the need to pursue a murder charge?" ABC News legal analyst Dan Abrams said today on "Good Morning America."

Court records show Fox served prison time for gun possession charges and auto theft in the 1990s. Fox also pleaded guilty in 2009 to a misdemeanor battery charge against Ogara, and was ordered to participate in a year-long domestic violence recovery program, in addition to probation.

The probation and a limited protection order against Fox expired in January.

"The best case scenario for him as this case moves forward is that jurors and prosecutors feel sorry for him and say this is a guy that clearly didn't mean to do this and is completely heartbroken," Abrams added.

Fox, Ogara and some friends had been drinking late Monday night, and Fox allegedly went outside and lit the cannon filled with explosives.  The barrel of the device exploded, sending shrapnel flying through the air. One piece of shrapnel went  through the wall of the trailer, hitting Ogara in the chest,  ABC News affiliate KGTV in San Diego reported.

Fox is also charged with the explosion of a destructive device and child endangerment. The couple's 4-year-old daughter was in the trailer at the time and was not hurt. She is now staying with her grandparents.

Fox, who is being held on $3.5 million bail, faces a possible life sentence without parole if he is convicted.