The judge had asked members of the jury if they could reach a consensus within a reasonable amount of time. When they said no, the judge declared the case a mistrial.
Carlile had been on trial for the death of his 7-year-old daughter. Prosecutors said Carlile left a loaded gun in his van with his four young children. His 3-year-old son grabbed the weapon and unintentionally shot and killed his sister.
Carlile's attorney, who called the incident a tragic mistake -- not a crime, said the jury, though split, was leaning heavily in Carlile's favor.
"It came down to the question of criminal negligence. The majority of the jury felt that there was not criminal negligence, and it was not a crime; it was a mistake, one of those momentary lapses," said defense attorney David Allen. "It was 7-4-1, so it was very strong in our favor."
The attorney said Carlile and his family have suffered immensely since losing their daughter.
"Derek accepts responsibility and is at fault for leaving a firearm in his car on March 10. There's no question about it; Derek screwed up. He knows that," said Allen. "They have faith in the system ... and they're hopeful, as we are, that the case will be dropped and they can go on living their lives."
The prosecutor said Carlile knew his son was fascinated by guns, and as a police officer, understands firearm safety better than most.
"No reasonable person would leave a loaded unsecured gun in a van with four children," said Lisa Paul, the prosecutor handling the case.
The prosecutor will review the evidence in the case before deciding whether to retry Carlile.