Preparing as an Expert Witness: Then and Now

Robin Cotton has testified as an expert witness in 35 states. Here, she describes what testifying was like in the early days of DNA, shares tips for how to simplify complicated terms for the jury, and explains why it’s important to speak to the science, no matter who is asking the question.





My name is Robin Cotton. I’m a biochemist by training. I have a PhD in molecular biology and biochemistry from UC-Irvine, and I got that PhD when I was a little older than most people getting a PhD, and then I did two post-docs. And, at that point, I wasn’t having fun. I wasn’t having fun in the lab I was in (I was at NIH). I mean, it was ok, but it wasn’t great, and a chemist friend of mine brought a newspaper clipping to me from The Washington Post, and the newspaper clipping had a little interview with some people who were starting a lab in Germantown, Maryland that was going to do DNA identification. And I had been reading, because it was related to my research interests, the papers by Alec Jeffreys, so I knew what that was. And I thought, “You know, this isn’t working, over here, this NIH thing. Maybe I’ll call them.” And I did. And I said, “Well, you know, do you have any positions open?” And they said, “Yes, why don’t you come up and interview?” And I did. And I went. And for a number of years I thought, “oh, this was probably a mistake. You know, I’ve left research.” But I never quit.

It was exhilarating to be able to take the science that you knew and apply it in this new vein, and do something that was helpful. And I never left, I just kept going.

We had a lab director who had been with ATF. He knew, and taught us, how to be fair, how to look at evidence, how to really consider it without considering the extenuating circumstances that you may or may not know.

I had a lot of good training from the early prosecutors – the early testimony with prosecutors. Because these were all big cases, people had to pay the lab to do the test, so they weren’t doing it on more trivial or run of the mill cases. They were doing it on homicides, and serial sexual assaults. And so the prosecutors that were working those cases were very good. They weren’t new people. And so I think I just sort of gradually more and more adept, because I had some good coaching at being an expert witness, and you also have to… If you want to do it, and you want to do it well, you can’t wing it. You have to sit down – like if I said when we switched from RFLP to PCR, I thought, “Oh, I know what PCR is.” First time I went into court and I tried to explain PCR, I’m like, “Oh my God. That was terrible.” So, what I did, and I’ve done a number of occasions, is sit down and say, “Alright, let me explain PCR. Fine, no problem.” And then sit down with that language, make sure I get rid of anything that’s not super important, and then take any scientific term and take it out and put a layman’s word in there instead. And so you have to do that, or something to that extent, and you have to practice.

So, I’ve testified in 35 states, probably about more than 250 times, and sometimes you just go like, “This is a pretty odd life skill to have.” Testifying in court? That’s it? I mean, I’m a pretty good scientist, but I’m not exceptional. I’m a pretty good manager, but I’m not exceptional. I’m a pretty good teacher, but I’m not exceptional. But I’m a really good expert witness, and that seems like a very weird thing to be good at!

And I’m teaching students now, and they’re coming in and they’re only looking at this new technology. So, it’s hard for them to have an appreciation of this big transition, and the thing that I think that they wouldn’t realize is how difficult the court situation was in the beginning.

So, there were admissibility hearings not in the occasional case, but in every case. In every state. In every case, no matter where we went early on, and it wasn’t just me. It was all the people from my company. All the people from two other companies. All the people from the early labs, like the FBI Lab that got started early, and the Virginia State Lab that got started early. Every place you went was a Frye hearing. Some of them very contested; some of them would last for days. So, you could not go in just to say, “Well, we extracted DNA” in this way that people now think of let’s make it simple for the jury and then just give them results, because the defense attorneys were hiring experts, they were asking long and detailed, and tortuous questions. The tactics of some of the defense attorneys are a little difficult. You know, somebody gets up in your face and calls you a liar; this is not really a fun experience. And yet, you are there to speak to the science, and you have to ignore that.

I get concerned, because you do hear people talk; as they’re talking about defense experts or they’re talking about defense attorneys as somehow these are not roles that one should aspire to, and that’s not really correct. And so, I began to understand quickly that, partly because of some of these exceptional prosecutors, that they had their role, the defense had their role, and that my responses to both of those people needed to be quiet, measured, and precise, no matter who was asking the question.