The retrial was supposed to begin Monday, Jan. 6. The judge has not set an exact date.
A judge was expected to decide whether future jurors will see thousands of text messages extracted from Armstrong's iPhone.
RELATED: A.J. Armstrong's lawyers bid to keep text messages out of retrial
The attorney for Armstrong filed a motion in December asking for Armstrong's phone records to not be allowed into evidence for the retrial.
According to court paperwork, Armstrong's team argues, because prosecutors lost Armstrong's iPhone at the end of his first trial, all records extracted from the phone should now be suppressed.
On Monday, ABC13 is set to air an exclusive interview with the accused killer. ABC13's Courtney Fischer is the only local journalist to have interviewed A.J. before both trials.
The mistrial happened in April after nearly a month of testimony from two dozen witnesses.
Judge Kelli Johnson told prosecutors and defense attorneys they are not to discuss this latest motion with media.
Armstrong is charged with murdering his parents, Dawn and Antonio Sr., while they slept in their southwest Houston home on July 29, 2016. Armstrong was 16 years old at the time.
During the first trial, more than 80,000 pages of phone records were entered into evidence. Prosecutors dissected hours of text messages between A.J. and his parent's timestamped from weeks and days leading up to their murders.
The state argued those messages showed Armstrong was angry with his parents because they took him out of private school. They had punished him by taking away his car and video game system due to his grades slipping.
Defense attorneys argued the messages between Armstrong and his parents were normal parent-teen conversations, showing a mother and father who wanted the best for their son.
Jury selection was supposed to begin Monday, Jan. 6.
"We're ready to go. I told you a while ago, we're excited to present this evidence to the 12 jurors. Looking forward, it sounds crazy, but I believe in A.J.'s innocence and I believe there are 12 people out there that are going to find him not guilty," said Armstrong's attorney, Rick DeToto.
The defense team won't discuss new strategies, but say it's possible the next jury will hear from new witnesses.
"It's expected it's going to take a little bit longer," said Chris Collings, another attorney with the defense team. "It's going to be a little more tedious."
FAMILY SHATTERED: The murder trial of A.J. Armstrong
CATCH UP ON THE A.J. ARMSTRONG CASE
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- 'I'M INNOCENT': Houston teen AJ Armstrong gives his side as he awaits trial in murder of his parents
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