Attorneys for Andres Segovia, 36, rested their case Friday morning after calling a radiologist to the stand.
But by Friday afternoon, Segovia had been found guilty.
Before that, radiologist Dr. Rebecca Loredo testified that she examined X-rays of Segovia's face several weeks after he was arrested for the June 8, 2012, murder of Joel Flores.
"There was a 3-millimeter size foreign body projecting over the soft tissues of the right face just below the level of the right orbit," she testified.
Flores, 32, was shot and killed after answering Segovia's call to come out of his parents' apartment and face him.
The men's families had been involved in an ongoing feud since the previous January when they were involved in a bar fight over a woman.
His lawyers suggested that the doctor's report showed that he may have been hit by shrapnel from other shots fired that night.
They rested without calling Segovia to testify.
The reason, said attorney Tony Jimenez, was that in his opinion the state had not proved its case beyond a reasonable doubt.
The punishment phase in Segovia's trial will begin Monday.