The Last Straw (36 page)

Nevertheless, despite all of that adrenaline-pumping action, she would have been hard-pressed to remember a more exciting time than when she’d finally seen that little white band appear and proven her supervisor’s hypothesis to be true. The thrill was matched a few months later, when the same photograph was published in
The Journal of Cell Biology
with her name listed as second author.

Shaking herself out of her reverie, she carried on scrolling through the document, before finally finding what she wanted in the ‘Materials and Methods’ section. Jotting down some notes, she quickly scribbled down some back-of-envelope calculations. The results were encouraging, but she knew to be cautious. Science moved on at a breakneck pace and what was state-of-the-art now was old news in just a few short years. She would need evidence to prove her idea — and that would have to wait until tomorrow.

Standing up, she felt the stuffiness of the room again. To hell with it, she suddenly decided, in a celebratory mood. She might not be able to afford an air-conditioning unit — and wasn’t sure where she would get one anyway at nine on a Wednesday evening — but Tesco had twenty-four-hour opening and she could afford to splash out on a fan. Not only that, she decided, I’ve been looking forward to starting that book all week and that rosé wine needs to be drunk. But I draw the line at getting a cat.

Thursday

Chapter 38

Eight a.m. the following day, DC Karen Hardwick took several deep breaths and tried to stop her hands shaking. The scribbled notes that she had written the night before were damp from perspiration that had nothing to do with the heat. She could see that DCI Jones’ office door was ajar, a sign that he was in and could be disturbed. But was he the right person to talk to? He was the boss. There were two more ranks between her, a lowly detective constable, and Jones, a detective chief inspector. Ordinarily, Karen would have spoken first to a detective sergeant or perhaps Detective Inspector Sutton. However, she had seen the faces around the table yesterday and realised that what she was about to suggest might not be popular.

Sod it, she decided. Time to bite the bullet. Jones seemed a sympathetic boss and he had actively sought her opinions a few times since asking her to accompany him Saturday morning. Screwing up her courage, she walked as confidently as she could to the office door. The administrative assistant nearest the door glanced up but said nothing, which Karen interpreted as ‘go ahead’; if Jones was busy or on the phone she would doubtless have said something.

With as much confidence as she could muster, Karen knocked twice.

“Come in.” The voice was confident but sounded a little scratchy, Karen noticed.

Opening the door, Karen stepped in. She had deliberately dressed in her most businesslike clothes this morning. A modest grey skirt that came to just above the knees, a white, short-sleeved silk blouse and a pair of smart black, flat shoes. Her hair had been teased into a bun and she wore just the barest hint of make-up. If Jones noticed, he didn’t give any indication and it was clear that he hadn’t given quite as much attention to his appearance that morning.

His face was sallow, with pronounced circles underneath his eyes. Although he was clean-shaven, Karen noticed that he appeared to have missed a few patches around the bottom of his throat. He wore what appeared to be a freshly starched light blue shirt, rather than the white one that he’d been wearing the day before, but the tie appeared to be the same and the dark jacket on the back of his chair looked a little creased. As Karen approached the desk she noted that his aftershave appeared to be a little stronger than normal.

Perhaps he was coming down with a summer cold, she thought. Then she remembered the appearance of DI Tony Sutton this morning, who had also looked decidedly dishevelled. Jones had grabbed Sutton and hauled him out of the office mid-afternoon the day before, saying something about going to the pub. Interesting…

“Yes, Karen, what can I do for you?” asked Jones, stifling a yawn.

Taking a few deep breaths, Karen plunged straight in. “I’ve been doing some thinking and a few things just don’t add up, sir. I think there may be more to what happened Friday night than we thought.”

Warren contemplated her for a second, before gesturing at the visitor chair in front of the desk. “OK, what’s on your mind?”

Karen sat down and spread her notes in front of her. “It’s Tom Spencer and his account of what happened on Friday night. I’ve been thinking about his trip to the PCR room and something doesn’t make sense.”

Warren motioned for her to continue.

“First of all, what was the weather like Friday night?”

Warren shrugged. “Hot and sticky, just like it has been for the past week.”

“And would you say that it was like that in the laboratories and offices in the Biology building?”

“I would imagine so. I don’t think that they have any air conditioning except in places like the PCR room.”

“What was Tom Spencer wearing when he found the professor’s body?”

“Jeans and a T-shirt, with a lab coat on. Why do you ask?”

“Well, do you remember how cold it was in the PCR room when Dr Crawley showed us around?”

Warren nodded, remembering how he’d been glad of his jacket. “I remember Crawley joked that the university looked after the equipment better than the staff.”

“Well, according to the computer log, Spencer was in the room for sixty-eight minutes. If I was in that room for so long, I’d probably have brought along a sweater or jacket to keep warm, especially if I’d been working in stuffy conditions all day. The contrast would have been uncomfortable to say the least.”

Warren frowned. “I can see where you are coming from, Karen, but maybe he forgot. Hell, it’s been like this for at least a week — he probably didn’t remember to bring a sweater to work. I guess he just had to grin and bear it. The room was cool, but I doubt he was in any danger of hypothermia.”

“Well, that’s the thing, you see — he didn’t have to grin and bear it. He could have left at any time.”

“I don’t follow you.”

“Spencer stated that he was doing a PCR reaction and that he used the Tetrad PCR machine. Well, the thing with PCR reactions is that you just set them up and then leave them to go. The whole process is automated. Spencer will have made up the solutions in his laboratory, placed his tubes in an ice bucket, then carried them down to the PCR room — witnesses did say that he was carrying an ice bucket. All he needs to do then is place the tubes in the machine, select the correct program, press start, then return when the run has finished. There is no reason to stay in a cold room for so long.”

Warren looked into space for a moment, his mind buzzing furiously.

“OK, playing devil’s advocate, maybe he did something else in there. Perhaps he was just on the skive, reading a magazine or something.”

“Sir, it was nine o’clock on a Friday night. The building was empty. It would be pretty unlikely that he would be found out if he was reading a magazine. And I’m sure he could have found somewhere else more comfortable to read. Besides which, there’s more.”

Warren raised an eyebrow. “Go on.”

“You said that he was wearing a face mask?”

“Yes, one of those sterile surgical masks. There was a box of them in the lab.”

“I don’t know why he would be wearing a mask. The chemicals used in PCR are harmless, certainly at that dose, so he wouldn’t have needed protecting.”

“Maybe it was to stop contamination of his samples — you know that Scenes of Crime Officers always wear them.”

“Possibly, but the thing is that, from what I understand, Tunbridge’s lab worked exclusively on bacteria. Any human DNA getting in the mix wouldn’t interfere with the reaction as it wouldn’t be recognised. Besides which, a few stray human cells with their DNA molecules locked away in the nucleus would be swamped by the pure bacterial DNA that he was probably using in his experiments. I rarely saw anybody wear masks when setting up standard PCR reactions. Some folks didn’t even wear gloves, although that’s frowned upon unless you have a latex allergy.”

Warren contemplated her for a long moment. “It’s an interesting thought, Karen, but it’s all very circumstantial. Maybe he was already wearing it because of something else he had been doing earlier. He already admitted that he had simply forgotten to remove his gloves.”

Karen nodded; she wasn’t a fool. “Well, I can only speak from personal experience, but I know that I hate wearing those face masks and can’t wait to take them off when I no longer need them.

“Regardless, they always told us in training that nothing is insignificant and that it’s your job to decide what’s important. Besides which, it’s not just those things. The timing doesn’t really add up. I don’t think he was in there long enough.”

“First you say he was in there too long, now you say not long enough. You can’t have it both ways.”

Karen flushed slightly. “That wasn’t what I meant, sir. I mean that if he was just popping in to set up his PCR reaction before leaving, he was in there far too long. But if he decided for whatever reason to see his program through to the end, he probably wasn’t in there long enough.”

“How long is long enough?”

Karen looked a little uncomfortable. “It’s hard to say, but I used to do a lot of PCR when I was a graduate student. The length of time needed varies a lot depending on what you are trying to achieve. And I have to point out that I did my masters degree a few years ago, and technology may have changed since then. But if my sums are reasonable, he was definitely in there too short a time.”

“OK, well, talk me through your reasoning.”

“First of all, sir, what do you know about PCR and DNA?”

“Probably a lot less than I should. I’ve heard the terms but, I’ll be honest, I don’t really understand them beyond how useful they have become to forensics. My wife is the biologist in the family, not me. Play it safe and assume I know nothing.”

“OK, let’s start with DNA.” Karen drew two parallel lines on the back of her notes. “As I’m sure you already know, the DNA molecule is composed of two strands, coiled around each other in a helix.” Warren nodded.

“Well, forgetting about the helix for a moment as it isn’t relevant, you can imagine DNA as like a ladder. Two vertical bits with rungs. Now imagine if you took your ladder and cut down the middle of each rung, leaving the half rungs sticking out of the vertical bit, a bit like a comb.”

Warren nodded again; Karen’s diagram made it clear.

“Unlike a ladder, however, each of those half-rungs is one of four different types of chemical called a base, referred to by their first letters, A, T, G and C. These four bases are like the letters of an alphabet and just like the way that the order of the twenty-six letters of the Roman alphabet can be arranged to provide an infinite number of different sentences, so can the four letters of DNA. The cell translates this code into the proteins that it needs to perform all of its jobs, in the same way that you translate the letters of the alphabet into a meaningful sentence.”

“With you so far. I remember this from a training course.”

“Well, remember that I said it was like a ladder, cut down the middle? Each of those rungs is made up of two bases joined together. However they can only join up in a particular way: A must always be joined to T and G must always be bound to C. So if you have a sequence of ATCG on one side of the ladder, then the opposite side of the ladder must be TAGC.”

To illustrate her point, Karen drew out the letters on the piece of paper

A T C G

T A G C

“We call each of these pairs a ‘base pair’. Humans have about three billion base pairs of DNA.”

“OK, I’ve got you. Now what is this PCR thing? I know it’s important in forensics, but I don’t see why Spencer would be using it — he works on bacteria.”

“Well, sir, first of all you have to remember that DNA is DNA. It doesn’t matter if it comes from humans, plants, bacteria, viruses or whatever, so PCR can be used on anything. But basically, the Polymerase Chain Reaction, or PCR, is a way of increasing the amount of DNA that you have to make more. What’s more it can be very specific, so that you only amplify the bit of DNA you are interested in and ignore the rest.”

“You’ll have to elaborate a bit more here, I’m afraid.”

“I’m sure you’ve seen shows like
CSI
where they take a single hair follicle and from that they are able to extract the DNA and perform loads of different tests?”

Warren snorted. The so-called ‘CSI effect’ had raised the public’s — and for that also read juries’ — expectations to unrealistic levels. The public expected results in hours rather than weeks and seemed to think that every crime scene, regardless of its triviality, should be subjected to thousands of pounds’ worth of DNA analysis.

He gestured for her to continue.

“Well, the fact is that in most samples the amount of DNA is minuscule; far too little for scientists to do anything meaningful with. So they need to make more of the DNA; millions of times as much. At the same time, they can make sure that they only make more of the DNA that they are interested in. In the human being, for example, scientists might only want to look at a thousand base pairs, so they only amplify that DNA, ignoring the remainder of the three billion base pairs.”

“OK, I can see why PCR is so important, but how long does it take?”

“That varies a lot, but I can do some estimates.”

Karen turned over another sheet of paper.

“The process has a number of steps. First you prepare all of the chemicals back in your lab and dispense it into tiny plastic tubes, which you can then carry down to the PCR machine in an ice bucket. Next you place the tubes in the PCR machine — more properly known as a thermo-cycler, because its job is to change temperature very rapidly. If you want to know how long Tom Spencer should have spent in the PCR room, this is when the clock starts.

“First step, is to heat the DNA to ninety-five degrees Celsius for about five minutes. This is enough to split the DNA ladder down the middle of the base pairs, leaving unpaired DNA bases sticking out like teeth in a comb.