The jury received the case Wednesday afternoon after hearing A.J. Armstrong's defense lawyers and state prosecutors make their closing arguments.
Over the 11 days of testimony, jurors heard a complex weaving of stories presented by prosecutors, who presented phone records, A.J.'s interrogation and 911 calls to illustrate a teen who was frustrated with his parents.
Defense attorneys countered with a suggestion that A.J.'s brother Josh committed the close-range shootings of Antonio and Dawn Armstrong.
"Where is Josh?! At least go interview him. At least have Daignault go talk to Josh. Find out what his situation is. What is his story? Was he involved? Was he not involved? Where was he? Who was he with? We'll never know. Because they made that decision. Because up until now, they have yet to interview Josh again or make any attempt to find out what happened. That's reasonable doubt because they don't want to know," Rick Detoto, A.J.'s attorney, implored to jurors.
The theory was quickly dismissed by prosecutors.
"There's no mystery, there's no phantoms, there's no Josh. We don't have to show you the motive, but you understand it. These people took everything from him and he didn't like it. And he didn't explode. He planned it. And he practiced it. And he lied about it," said John Brewer, Harris County prosecutor.
Prosecutors said the Armstrong house alarm shows the killer had to be in the home the night of the murders. Armstrong's team insisted the security system is unreliable.
Defense attorneys also claimed police never looked for a killer outside the home. They pointed out that within 11 minutes of entering the family's home after the killings, A.J. was handcuffed.
Attorneys also told the jury that no physical evidence linking A.J. to the killings was found in the home.
"And based on everything we've talked about in this case, with all due respect, find Antonio Armstrong (Jr.), A.J., not guilty in this case," said Detoto.
"I've seen a lot of evil in my days. But I tell you, ladies and gentlemen of the jury, it's the evil you don't see coming that is the worst evil of all," countered Lester Blizzard, a Harris County prosecutor.
While the jury only got a handful of hours to deliberate Wednesday, there is no telling how long it will take jurors to decide on his guilt or innocence. Nevertheless, jurors continue deliberations at 9 a.m. Thursday.
In all, nearly 40 witnesses took the stand and dozens of pieces of evidence were presented.
WATCH: Top moments of A.J. Armstrong trial closing arguments
JULY 29, 2016 - THE MURDERS
Inside the townhome of Antonio and Dawn Armstrong, the couple, who were owners of a gym in the Bellaire area, were found shot in their bedroom. Both sustained wounds to the head.
Dawn had died when police arrived at the scene. Antonio, who had played professional football and then retired to become a trainer and motivational speaker, held on but was slipping away as hours passed.
Police were informed of the shootings through a phone call to 911 by their 16-year-old son A.J.
Investigators were told by A.J. an intruder pulled the trigger, but they later found nothing out of place inside the home and no signs of a scuffle.
Police also stated A.J.'s sister was at home at the time of the shootings.
A.J. was taken into custody, charged with capital murder.
WATCH: AJ Armstrong's aunt testifies before defense rests case
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