She and her father gave authorities samples as part of an effort to identify eight of Gacy's victims more than two years ago and learned none of the remains were those of her sibling, 22-year-old Edward Beaudion who went missing in 1978.
Eventually, the work done in the Gacy probe did help provide the family with some answers they had long awaited: Beaudion's remains were those found in a forest preserve by hikers in 2008. And his killer was a small-time Missouri crook named Jerry Jackson who died last year.
On Wednesday, Rodriguez and her 86-year-old father, Louis Beaudion, appeared with Cook County Sheriff Tom Dart to announce the news.
"My mom went to her grave in 2001 not knowing where my brother was," the sister said. "My dad, he will now be able to know where my brother was."
She said Edward Beaudion's cremated remains will, upon their father's death, be placed in the dad's casket next to their mother's.
Authorities don't know exactly how Beaudion died because his skull was never found. But Dart explained what investigators do know.
Beaudion was driving his sister's car on July 23, 1978, when he dropped a friend off and told her he was heading home. No one ever heard from him again.
Weeks later, Jackson was taken into custody in Caruthersville, Mo., after he was found driving the car, which Beaudion's family had reported stolen. Jackson was trying to sell stolen items at a pawnshop, Dart said.
Jackson was extradited to Chicago, where police said he told them he had met Beaudion in downtown Chicago on the day the man disappeared and knocked him unconscious with a punch to the face during an altercation. Police said he told them he stuffed Beaudion's body in the car, drove to a wooded area about 15 miles southwest of Chicago and dumped it.
But when he took police to the area, the search came up empty and police only charged him with auto theft, a crime that led to a four-year prison sentence for Jackson.
Then in 2008, hikers found a partial skeleton in a forest preserve — in the same general area where Jackson had taken police years before — but the investigation went nowhere. The bones, one of which had an orthopedic screw in it, were taken to the county medical examiner's office.
Three years later, Dart's office exhumed eight of Gacy's unidentified victims from the 1970s to test DNA. Dart asked relatives of young men who disappeared at the time of Gacy's killings to submit DNA samples for comparison.
The second call they received in response to their request came from Rodriguez. Not only was her brother the age of many of Gacy's victims, but the family's home was just a few miles from Gacy's.
Meanwhile, sheriff's detective Jason Moran was working with the medical examiner's office to clean up the operation in the wake of revelations about stacked bodies and remains tossed haphazardly in boxes. Dart said the medical examiner's office did send some bones out for testing but "failed to look in one closet" where Beaudion's bones were stored.
Ultimately, the medical examiner's office shipped the unidentified bones to the same lab where Moran had sent DNA samples of Beaudion's relatives in the Gacy case. And earlier this year, the lab reported a "genetic association" between those bones and DNA from Beaudion's relatives, who also confirmed he'd had an orthopedic screw in his knee.
Beaudion is the latest of at least three people whose remains have been identified as part of the Gacy investigation. Besides identifying one of the eight exhumed Gacy victims, the effort also led to the identification of the remains of a 22-year-old man found in Utah, and the identification of bones found in New Jersey as those of a teenager who disappeared in 1972.
Rodriguez and her father said they're disappointed Jackson died before he could be brought to justice for Beaudion's slaying. Sheriff Dart said it would have been a strong case.
A few weeks ago, he and detective Moran saw for themselves what the identification meant to Beaudion's father and sister when they took them to where the bones were found. After Dart had the dense brush cut away so Louis Beaudion could reach the spot, he and Moran watched as the elderly man revealed what he'd been carrying under his arm.
"He starts crying and opens a bag that has a cross in it (and) he gets down on one knee and with a little hammer pounded this cross into the ground," Moran said. "This guy, 36 years after his son is killed, he's crying like he went missing yesterday and then he grabbed my arm and said, 'Thank you.'"