The Philadelphia Police Department's analysts say Rudolph Churchill's DNA is a "match" for that on two items found near the bodies of two North Philadelphia women raped and slain in 1989.
A defense DNA expert says match is too imprecise a word, and the best she can say is that Churchill "cannot be excluded" as the person who left that DNA behind 27 years ago.
The scientific chasm between those conclusions - and whether the DNA proves beyond a reasonable doubt that Churchill killed Ruby Ellis and Cheryl Hanible - will soon be up to a Philadelphia jury of eight women and four men to bridge.
The debate about the state of forensic DNA science consumed most of Thursday's session in Churchill's trial for rape and murder.
It will likely consume most of Friday as well, when Katherine Cross, a DNA expert from Abington-based Guardian Forensic Sciences, continues being questioned by Assistant District Attorney Andrew Notaristefano.
Cross, whose firm was retained by defense attorney Gina Capuano to review the DNA evidence prosecutors say proves Churchill killed the women, was the first defense witness to testify.
Assistant District Attorney Gwenn Cujdik ended the prosecution case earlier Thursday after additional testimony from police DNA analyst Bryne Strother.
The interpretation of DNA evidence is likely to dominate the remainder of the trial. As Cross testified, Strother and other representatives of the police DNA lab listened, and Cudjik said she would likely have rebuttal evidence.
The defense case began with Churchill, 54, of Paulsboro, telling Common Pleas Court Judge Rose Marie DeFino-Nastasi that he would not testify in his defense.
Under the Constitution, criminal defendants are not required to testify or present any evidence, and the judge will instruct the jurors they may not consider that decision in reaching a verdict.
Ellis, 19, was discovered dead on March 17, 1989, inside an abandoned car near 15th and Thompson Streets. On April 23, 1989, the body of Hanible, 33, was found in a burned-out bar on the 1200 block of West Girard Avenue. Both women were addicted to drugs and worked as prostitutes to feed their habits.
The case was unsolved until 2013, when Philadelphia police, testing for DNA in cold case homicides under a federal grant, came up with a match for Churchill in an FBI database.
Churchill, who at the time of the slayings lived in the 1300 block of Ridge Avenue in North Philadelphia, a few blocks from where both bodies were found, had not been a suspect.
But in 2013, police learned of a DNA match to a sample Churchill was required to give when he was released in 2007 after serving three years in a Georgia prison for burglary.
The prosecution alleges that Churchill's DNA is on two pieces of evidence: a bloody paper towel found in the car near Ellis' body, and on Hanible's sneaker.
Strother testified Wednesday that Churchill was the sole source of the DNA on the paper towel. She said the DNA on Hanible's left sneaker came from up to three people, at least one of whom was male.
Strother said that based on a sample of Churchill's DNA, he was 629,800 times more likely to have deposited it there than any other unrelated African American male in the general population.