The dead woman's mailman had to take a polygraph test after lying to investigators about having sex with her.
Her teenage daughter had to undergo a lie-detector test, too. She stood to receive $500,000 in life insurance benefits after her mother and her mother's 15-month-old son were found dead on July 6, 2007.
But the two were eliminated as suspects in the St. Petersburg woman's death, as were a current and former boyfriend of Paula O'Conner's daughter.
Investigators then focused on Ralph Wright Jr., a sergeant at MacDill Air Force Base in Tampa, who was once O'Conner's fiance and, likely, the toddler's father.
Today, Wright, now 44, goes on trial in the deaths of 37-year-old O'Conner and her son, Alijah.
Pinellas-Pasco State Attorney Bernie McCabe is seeking the death penalty.
Jury selection is expected to take two days, and the trial could last as long as three weeks, prosecutors say.
Wright denies killing the pair, and also that the toddler was his son.
It was months before he was accused of strangling the woman and asphyxiating the child, possibly by smothering him.
According to thousands of pages of court documents, this is how investigators built their case against him:
O'Conner was a creature of habit. After she woke up at her well-kempt St. Petersburg home, she would let her two dogs a yellow Labrador named Dusty and a chocolate Labrador named Amber — out into the fenced backyard. Then she would get herself ready for work and Alijah ready for day care.
But on that morning about 51/2 years ago, O'Conner never made it to her job at an insurance company, and Alijah didn't get to the babysitter's. O'Conner's Chevrolet Blazer wasn't in the driveway at her house at 482 Dawson Ave. N.E., either.
By then, she had hired an attorney to help her prove Wright was Alijah's father and get child support. A private investigator had tracked Wright down a few weeks before to serve him court papers.
O'Conner also wanted financial help for Alijah's medical bills. Born with congenital heart defects, he had undergone three surgeries, and a shunt had been inserted into his skull to help with fluid leaking into his brain.
O'Conner was afraid Wright might retaliate and had her locks changed.
Along with hiring an attorney, she wrote the secretary of the U.S. Air Force and to U.S. Rep. C.W. Bill Young, R-Indian Shores, complaining of Wright, and created a website lambasting him, militarydeadbeatdads.com.
"I only hope Ralph does not try to make it hell," she wrote the private investigator, John Zurenda, in an email. "I won't be opening the door for him. That much I know.
"I am still nervous of him showing up at my house."
Once word got out that O'Conner and the boy were unaccounted for, Zurenda and O'Conner's then 18-year-old daughter, who had moved out, met at the house, which was locked. The pair used a screwdriver to take some hinges off a side door, and Zurenda went in.
Alijah was dead in his crib, his mother sprawled out on the floor of his room, also dead and naked from the waist down.
Wright quickly emerged as the prime suspect, and investigators tracked him to MacDill by late afternoon.
"That girl has been a thorn in my side," were the first words out of his mouth, a police report says.
He and O'Conner had met online in 2004, investigators learned, and he had promised to marry her, even though he had a wife and teenage son in Orlando.
O'Conner became pregnant. Wright suggested she get an abortion, but O'Conner wanted the child, court documents state.
Once he learned the baby had medical problems, he dropped out of sight, but O'Conner thought he was on a military mission in Africa.
In December 2005, O'Conner wrote to Wright, telling him she was struggling to make ends meet and asking him for money.
As it turned out, Wright never went to Africa. He was spotted directing traffic at the annual MacDill air show, and O'Conner was incensed. She ratcheted up her effort to force him to give her money.
Investigators believe that on the morning of the slayings, Wright parked his Ford Expedition a little ways from O'Conner's house, walked there, unscrewed motion detection lights at the back door and waited.
A military police officer with experience handling dogs, he grabbed O'Conner as she was letting the dogs out and dragged her through the house to Alijah's room, where he killed them both, one report says.
A neighbor heard screaming but thought O'Conner was fighting with her daughter, whom the neighbor didn't know had moved out.
The only evidence of a struggle was a clump of O'Conner's hair in the kitchen and a broken picture frame. There was no sexual assault, an autopsy showed.
After the slayings, Wright took O'Conner's Blazer, drove a few blocks to his Expedition, switched vehicles and drove back to Tampa.
But investigators say Wright mistakenly left something behind on the arm of the living room couch: a black size 8 glove typically worn by military pilots. Detectives believe he put the gloves on after killing the two with his bare hands, to ensure he didn't leave any fingerprints behind. But he had trouble locking the front door from the inside as he left and took one off, investigators say.
A shipment of 25 of the same gloves had arrived at MacDill the previous February, but Wright was deactivated by the time investigators checked with base officials, and any documentation that would have linked him to the type of glove had been destroyed.
Wright's DNA might have linked him to the glove, but investigators didn't have any samples, and Wright refused to volunteer any. They also needed Wright's DNA to prove paternity.
However, while he was under investigation at MacDill for being AWOL at the time of the double-slaying, Wright cut his finger and accidentally left a drop of blood on a form associated with the investigation, court documents say.
A lieutenant colonel offered him a shirt to wipe off his hand; that and the document with Wright's blood on it were given to a laboratory for analysis, and soon after investigators got a search warrant for Wright's DNA and fingerprints.
Laboratory analysts found Wright's DNA on O'Conner's neck and on the inside of the black glove. Alijah's DNA was also on the inside of the glove.
Wright was indicted by a grand jury late in 2008 and was arrested while he was making a delivery for UPS to Palatka. After he was read his rights, Wright agreed to talk.
He denied ever having sex with O'Conner and, when told his DNA matched Alijah's, he suggested O'Conner might have drugged and raped him, according to a 145-page transcript of the interview.
St. Petersburg police Detective Karl Sauer suggested O'Conner could ruin him financially, professionally and personally with her demands for child support and help with the medical bills for Alijah. The outstanding medical bills came to $357,000, and Wright also owed roughly $20,000 in child support.
Wright was already married, so his relationship with O'Conner would have constituted adultery, which is a violation of military code. While at MacDill, Wright had also dated at least two other women, in addition to O'Conner.
Wright was having none of it, though. As a reservist, Wright said he didn't have much of a military career to begin with. And a simple bankruptcy filing would have taken care of any new financial demands, he said.
While he admitted to the two other relationships, he continued denying ever having had sex with O'Conner, denied killing her, and said he couldn't see how anyone would kill a child.
"I got a soft spot for children," he said.