Brenda Smith with the Kern County Regional Crime Lab analyzed several items from the crime scene at the Harper family home. The results showed DNA from Vincent Brothers was present on a latex glove tip detectives discovered underneath the contents of Joanie Harper's purse in the laundry room (to see the laundry room, click on the photo gallery in the evidence locker). Prosecutor Lisa Green says Brothers used rubber gloves while committing the crimes to avoid leaving behind fingerprints. And an FBI agent testified in pre-trial motions that the killer took things out of cabinets and turned portions of the home inside out to stage the crime scene as botched robbery.
The analysis of the glove tip showed there were 3 sources of DNA on it. Smith called them "contributors" But there wasn't a lot of DNA on the glove, so Smith was not able to determine 2 of the contributors. Smith was not able to rule out Vincent Brothers as a 'major' contributor of the other DNA in the glove. That means there is a high probability the majority of the DNA is Brothers. Why can't we say for sure it's his?
Well, first a primer on DNA "fingerprinting." The chemical structure of DNA is the same for everyone. But the order in which the chemical elements (base paris) of DNA appear differs from person to person. Scientists look at small islands of DNA where there is a great deal of variation. In forensics, the DNA of an unknown sample (in this case a glove tip) is compared with a sample from the suspects and victims (in this case the Harper family and Vincent Brothers). If one "island" of the unknown DNA matches one of the "known" samples, there's a small probability it's the same DNA. But if you look at a lot of DNA "islands" and they are all the same, it increases the probability the known DNA is the same as the unknown. The probabilities can become so high (ie 1 in 6 billion) that they're admissible in a court of law. Still, we can't say for sure the DNA is Brothers' in this case.
What does the DNA evidence in this case tell us?
1. There was part of a glove tip found amid the contents of Joanie Harper's purse.
2. DNA isolated from the tip was most likely Brothers'.
What does the DNA evidence on the glove tip NOT tell us?
1. How did the glove tip get there?
2. When did the glove tip get there? Did it drop there before the murders, during the murders or after?
3. Who wore the glove? It's possible someone else wore the glove and touched things that Brothers touched while he was still living in the Harper family home with Joanie. Also, there's no way of knowing which side is the "outside" of the glove tip and which side is "in" That is, the DNA could have come from the inside surface of the glove, or been deposited on the outside.
4. How old was the DNA? The defense says the Harper family routinely used rubber gloves to clean the home. Is it possible Brothers could have worn the gloves while helping out around the home while he lived there?
This is what the jury will have to weigh.
Brenda Smith also swabbed and tested other household items for the presence of DNA: a cordless telephone base, currency, receipts, a baby monitor, a TV remote found on the bed near Joanie Harper's body, a JC Penny credit card found on the floor of the garage, and the hands of several of the victims.
The JC Penny card and Earnestine Harper's hands both revealed DNA that strongly matched Earnestine's DNA.
Several dollar bills sitting on a dresser, a phone base, and the TV remote all had DNA that strongly matched Marques Harper.
Each of the victim's hands had DNA that seemed to strongly match the victim.
Finally, shell casings from the crime scene surrendered only trace amounts of DNA. There were so few "islands" of DNA in the analysis that Smith didn't feel confident enough to make a comparison.
Prosecutor Green says she has two more witness to present. Their testimony could wrapup the week of April 2. The defense is up next.
