Polar Quest

22

Leslie Siwik and her husband returned home from Jackson Hole a little stiff but otherwise pleased with their annual week on the Western slopes. She switched on the kitchen television and, as she started to unload her suitcase in the laundry room, heard a news anchor announce the arraignment of scientist-entrepreneur Oswald Eames for the murder of his partner and ex-wife.

Siwik rushed back to the kitchen as the newscast moved on to a three-car accident on the Lodge Freeway. Flipping through the other local channels, she caught the story again, this time with Eames standing before the judge wearing an orange prison jumpsuit at his arraignment. Stunned, Siwik then grabbed her phone and hit the speed dial.

‘Please be there, please be there,’ she pleaded like a mantra.

‘Forensic biology unit,’ a voice answered after the sixth ring.

‘Art, thank God you haven’t gone home,’ Siwik blurted out. ‘It’s Leslie. I need you to do me a favor.’

‘I was just on my way out, but sure, what?’

‘Check the fridge in the Evidence Processing Area. I’m looking for anything that’s come in from that double homicide in Ann Arbor.’

‘The UGene thing?’

‘Yes. They’ve arrested Oswald Eames for it.’

‘No way! Not Oz,’ Art said, disbelieving. ‘Hold on, I’ll take a look.’

The line went silent and Siwik waited nervously for an answer. A moment later, she heard a click and Art was back.

‘Yeah, it looks like we got a couple kits and a blood draw.’

‘Thanks, Art,’ Siwik said, relieved. ‘Leave the lights on, I’m coming in.’

‘Should we even be handling this evidence? I mean, we both know Oz. Isn’t this some kind of conflict of interest?’

‘Not the way I see it. The crime happened in our part of the state, that’s why the evidence came to us. And every other state lab has the same problem we have regarding personal knowledge of the suspect; without UGene we’d never have cut through our backlog. We could send the evidence to the feds, but it could be months before we get an answer, all the while leaving Oz in limbo.’

‘But won’t the prosecutor try to nail you for personal bias?’

‘If I do my job right and keep the chain of evidence intact, no one will be able to refute my findings. This is DNA, Art, I either make a match or I don’t. The markers don’t lie.’

Siwik returned to the lab that night and went to work on the materials from the Olson-Sutton murders with a single-minded attention to precise laboratory procedure. Her aim was nothing less than a perfect analysis of the forensic evidence.

As with any jigsaw puzzle, Siwik began by sorting out the pieces. The blood drawn from the two victims and Eames provided proof of identity, while the two evidence collection kits contained proof of the crime. She knew the crime in question on the lab bench before her was not murder but rape, and, as the two acts in this case were inextricably linked, proof of one was enough to imply guilt in the other.

From the rape kit, Siwik tested the swabs for the presence of acid phosphatase, an enzyme found in high concentration in seminal fluid. She detected no color change in the swabs from Olson’s mouth and anus, but the vaginal swabs turned a pinkish purple color. She then applied the ‘Christmas Tree’ stain to the slides made from the vaginal swabs by the medical examiner.

Under the microscope, the epithelial cells swabbed from Olson’s vagina appeared like green fried eggs with bright red yolks. Intermixed with the cells were a tangle of sperm with bright green tails. The sperm cells’ red ovoid heads fluoresced under the light of the microscope, making it easy for Siwik to count the sperm cells present on the slide. The sperm count was good,providing more than enough DNA to identify the man responsible for leaving it behind inside Olson’s body.

She also compared the pubic hairs collected from Olson’s body with those pulled from Olson and Sutton. Most of the combed hairs belonged to the victim, but the remainder were similar enough for Siwik to conclude they came from one person, and that person was not Lloyd Sutton.

Through a process known as differential extraction, Siwik wrung the vaginal and sperm cells from one of the cotton swabs, then carefully separated the cells of the killer from those of his victim. She ruptured these cells with a lysing agent, causing them to disgorge their load of DNA, then ran both samples through a series of spin and rinse cycles. Each iteration refined and purified her samples of the precious coiled strands of genetic material.

After the last cycle, Siwik gently swirled a test tube freshly filled with Tris-EDTA. At the base of the tube, a small white pellet dissolved into the clear solution, and suspended in the preserving medium were the genetic blueprints of a man. As she stared into the tube, she prayed the microscopic strands would exonerate Oswald Eames.

She processed the blood samples in much the same manner as the cells harvested from the evidence collection kit. The case had yielded five distinct samples of DNA, four from known sources and one belonging to a murderer. Siwik’s interest lay not in the six billion base pairs of the human genome, but rather in thirteen much smaller tracts of short tandem repeats known in forensic circles as the FBI’s CODIS Core STR Loci.

Using a PCR machine, she amplified her samples, chemically replicating those selected tracts of DNA over and over until she had millions of tiny copies. Siwik loaded these into a 310 Genetic Analyzer and programmed the machine for an overnight run. In the darkness of the lab, the analyzer stretched out the tiny stands of DNA and meticulously read the STRs like supermarket bar codes with a ten milliwatt argon-ion laser.

On the morning of the fifth day of her investigation, Siwik returned to the lab and went straight to the genetic analyzer’s ink-jet color printer. There she found several pages neatly piled in the output tray.

Siwik first checked the report for her experimental controls, samples of test DNA that provide known results, and was relieved to find that she hadn’t screwed anything up and that the PCR machine had functioned properly. She then compared the chart for Olson’s blood with that of the cells recovered from the swab. It was a perfect match, proving that both samples had come from Olson. The result wasn’t unexpected, but it provided an additional check on her work.

In comparing Olson’s blood with her assailant’s semen, Siwik found no correlation for the core loci or the gender identifier, which meant that she’d successfully isolated the killer’s DNA from that of his victim and the sample of unknown origin bore a clean genetic fingerprint.

Setting Olson’s charts aside, Siwik compared Sutton’s profile to that of the murderer. Both men registered X and Y chromosomes, but the length of the STRs indicated two different sets of parents. None of the thirteen core loci matched, proving that Sutton did not have sex with Olson prior to their murders.

‘Now for you, Oz,’ Siwik whispered hopefully.

Siwik laid the charts from Eames’s blood sample on the counter next to those of the killer. She compared the first loci and her heart sank when she saw the match.

‘Easy, girl,’ she admonished herself. ‘That’s only one point. You’ve got twelve more to go.’

Point by point, she compared the two genetic profiles, and with each match found herself praying that the next would show something wildly different, something that would prove Oswald Eames’s innocence. After nine points, Siwik began to feel a sickening inevitability. She knew the odds, and with each match the probability that both samples had come from the same man grew exponentially.

Tears welled up in her eyes as she moved her fingers to the last of the thirteen loci. As with all the others, they were identical. Siwik felt horrified and betrayed. The graphs illustrated the inescapable conclusion that Oswald Eames — a man she knew and liked, a brilliant scientist whom she viewed as both colleague and mentor — was guilty.