Former "American Idol" contestant Caleb Flynn's missing handgun sent investigators into storm drains with a high-powered magnet, underneath vehicles and through attic insulation as they searched for the weapon prosecutors allege he used to kill his wife.

Despite the extensive search, investigators never found the gun, a Tipp City detective testified Monday during Flynn's murder trial in Ohio.

Flynn is accused of fatally shooting his wife, Ashley Flynn, inside the couple's home on Feb. 16 before staging the scene to look like an intruder had broken in. He has pleaded not guilty to aggravated murder and other charges.

The trial turned deeply personal Tuesday as Ashley's mother and sister took the stand, describing the family's frantic first hours after her death and the stunning revelation that Flynn had allegedly been having an affair with a woman they knew from church.

Ashley's mother, Jill Smith, testified that her phone rang around 3 a.m. the morning her daughter was killed. She initially thought it was her husband, who was traveling, but saw Flynn's name on the screen instead.

"She's gone," Smith recalled Flynn telling her.

When Smith asked who he meant, Flynn responded, "Ashley, she's gone," before telling her, "Someone broke in and shot her," she testified.

Smith said she told Flynn she was coming to the house, but he told her police were there and she could not come. She hung up, became dizzy and lay down on the bathroom floor.

"It seemed like forever," Smith testified, saying she remained there for about five minutes before getting up and calling her husband to tell him Ashley had been killed.

Smith drove to the home anyway and said seeing the flashing police lights made the reality of what had happened sink in.

"And then I knew it was true," she testified.

Flynn later came outside shaking, Smith said. The two hugged before sitting on the front porch, where she became concerned enough about him that she asked for a blanket and suggested someone call an EMT because she feared he was going into shock.

Ashley's sister, Kayla Keyt, testified that she initially believed so strongly in Flynn's innocence that she told investigators "100%" they had arrested the wrong man.

"I trusted Caleb with everything I had in me," Keyt testified.

Keyt said she became angry when she initially heard rumors that Flynn had been having an affair because she believed they were unfairly damaging his reputation.

"I was so mad because it was tarnishing his reputation," Keyt said. "I just knew in my heart that he was completely innocent. I really believed that with all of my heart."

Keyt testified that changed when investigators told her Flynn had been having an affair with Alleigha, a woman the family knew from Christian Life Center.

Alleigha was the church's main worship leader and performed alongside Flynn, who sang with the worship team during rehearsals and weekend services, Keyt testified. She said she personally knew Alleigha casually from seeing her at church.

"I don't think I've been more shocked in my life," Keyt said.

Keyt recalled asking investigators, "Are you 100% sure?" and said she had them repeat it two or three times because she "could not even fathom" Flynn having an affair. She testified that she first learned about it during an FBI interview the morning after Flynn's arrest.

Keyt, who testified that Ashley's two daughters now live with her family, said the girls have since learned about the alleged affair and personally knew Alleigha.

"They were mostly brokenhearted for mommy," Keyt testified.

Keyt said the girls were shocked and questioned why their father did not love their mother as much as Ashley loved him.

But when the girls were told who Flynn had allegedly been involved with, Keyt recalled the older daughter's response: "I'm not surprised."

The emotional testimony Tuesday followed a day of forensic evidence and testimony about investigators' exhaustive search for the missing gun.

Detective Adam Bernard walked jurors through the lengths investigators went to as they searched for the missing firearm in the days after Ashley's death.

Police searched the backyard and nearby wooded areas before turning their attention underground, where investigators used a high-powered magnet to search storm drains along several streets.

Bernard testified that investigators removed the drain covers, lowered the magnet inside and swept connecting pipes before he physically climbed into accessible culverts with a flashlight to search areas the magnet may have missed.

They found nothing.

Investigators later had both vehicles from the Flynn home placed on lifts so they could search underneath them and other areas where something could have been hidden, Bernard testified. That search also came up empty.

Police even rented equipment to remove insulation from the attic as they continued looking for the gun.

Bernard testified that investigators also tried to trace Flynn's firearm purchase history after Flynn previously said he bought a gun in South Carolina, where he obtained his concealed-carry permit.

The detective said he called nearly two dozen gun stores in the state looking for records that could identify the make, model and serial number of a firearm purchased by Flynn.

That effort did not identify a gun tied to Flynn or Ashley.

The testimony came after a forensic pathologist walked jurors through Ashley's autopsy and described two gunshot wounds to the back of her head.

Dr. Bryan Casto testified that the entrance wounds overlapped, and the bullets traveled through Ashley's head on nearly parallel paths. One of the bullets exited her head before reentering her left arm near the elbow, where it was recovered during the autopsy.

Casto said the wounds and the paths of the bullets suggested Ashley was shot at close range, but he could not say exactly how far away the gun was when it was fired.

The pathologist determined Ashley died from multiple gunshot wounds to the head.

Earlier Monday, Ohio Bureau of Criminal Investigation (BCI) crime scene investigators walked jurors through evidence collected throughout the Flynn home as prosecutors sought to show the alleged break-in had been staged.

A BCI crime scene technician who had examined between 20 and 30 forced-entry doors testified that the damage to a side garage door did not look like the forced entries she had previously investigated.

She said the damage was on the inside of the door rather than areas she would typically expect to be damaged if someone had kicked or pried their way inside.

Flynn's defense challenged the state's conclusions on cross-examination, pointing out that investigators could not determine when some of the door damage occurred and that no blood-spatter analysis was performed because conditions at the scene were not suitable for one.

David Hammond, a senior special agent with BCI, also testified that he was not aware of evidence showing blood spatter from Ashley's shooting on Flynn's clothing.

The defense later pressed Bernard about tips received after the killing, including one from a caller who referenced an alleged "hit."

Bernard testified that he printed tips received by Tipp City police and passed them to the FBI for follow-up. He said he did not know whether the FBI investigated that particular tip.

The judge sustained objections when the defense tried to get into some of the caller's specific claims.

Prosecutors also laid the groundwork Monday for the massive trove of messages they say Flynn exchanged with his mistress.

Bernard testified that a search warrant served on Microsoft produced 107,655 lines of data associated with an email address belonging to Flynn.

The records were admitted into evidence over a defense objection.