In the hours and days after finding the body of Frances Bloomfield in a ditch outside Rockford, Ill., on Sept. 22, 1997, investigators collected hundreds of pieces of evidence.
Boxes of duct tape from her Iowa City home, maps of Minnesota from inside her car, along with ligatures and plastic used to wrap and bind her body, were among items police amassed in hopes of finding her killer.
None of the evidence immediately produced a suspect, but thanks to the ever-advancing field of forensic technology, this week it did. Using a relatively new tool that analyzes only the Y chromosome portion of a DNA profile, detectives have discovered evidence linking Bloomfield’s husband, John R. Bloomfield, 73, of St. Paul, Minn., to the homicide.
But the “Y-STR” DNA evidence that police cited as part of their justification for Bloomfield’s arrest is not the same as a traditional DNA profile match, said Sabrina Seehafer, DNA criminalist for the Iowa Division of Criminal Investigation. Because, she said, every male in a family line would have the same Y-STR profile.
“The statistical power of this analysis is much more decreased,” Seehafer said. “If you have a father, a son and an uncle, all three of those should have the same Y-STR profile.”
If police find a fairly complete DNA sample at a crime scene, the likelihood of two people matching can be as rare as one in one billion. For a Y-STR match, Seehafer said, the likelihood of a match is more like 1 in 1,000.
“This is a different statistical model,” she said.
In the Bloomfield case, a Y chromosome profile pulled from one of the ligatures used to bind the victim’s body came back “consistent” with John Bloomfield’s Y chromosome, according to a criminal complaint. The complaint laid out additional evidence that led to his arrest – including a possible motive, lack of alibi, inconsistent stories and a hair located on tape from Francis Bloomfield’s body was found to be microscopically similar to her husband’s hair, according to police.
Investigators decided to run the old evidence through the new Y-STR test based on a finding of male DNA on the binding, according to police. DNA experts say “Y-STR” DNA analysis has been around for about five years and is most useful when there is a mix of male and female DNA.
The Iowa DCI lab doesn’t perform Y-STR analyses due to limited resources, said Bruce Reeve, laboratory administrator.
“But it’s on our list of things we want to be doing here,” he said. “It’s pretty high on our wish list.”
Authorities declined to comment on details of the DNA testing in the Bloomfield case, but Iowa City police Sgt. Vicki Lalla said "technological advances in the intervening years between when the murder was committed and today played a big part.”
Reeve said that both the FBI and private laboratories can conduct the Y-STR analysis.
“If we had a cold case come into the lab where we felt a Y-STR would help, we would refer that case out to other agencies,” Reeve said.
The DCI has recently added some new forensic tools to its repertoire, including new software to its fingerprint and ballistics databases. The new fingerprint software allows for better searches, Reeve said, and the new ballistics software operates using three-dimensional technology.
“They are getting better at mining information out of the database,” he said. “And in the instance of the fingerprint software, we actually are asking agencies to consider resubmitting evidence from unsolved violent crimes.”
Still, even with the new technology available, Reeve said it can take time to identify cases where it would be helpful, find resources to run new tests and then actually perform the analyses.“You need resources to go back case by case to see if there is evidence that we could apply new technology to,” he said. “But (advancing forensic technology) has been a big boon to cold cases over the past several years.”