How Did the DNA Get There? The Science Behind Activity Level Propositions in Forensics

Laura: Ray Ashley, thank you so much for joining us here at ISHI. Our 35th anniversary. We’re really honored that you were here to do a presentation for us and are taking time out for this video. Before we get into touch DNA, what you spoke about, maybe you could each give us a brief introduction to, you know, talk about your professional background and what brought you here.

Ashley: Okay. Um, my name is Ashley Hall. Currently, I am the director of the forensic science graduate program at UC Davis. I came here after grad school. I went into the defense industry for about five years. Became a bit disenchanted, moved into academia. I’ve come through two big ten tier one research universities, Nebraska and Illinois, until I landed at UC Davis. Now, my research focuses on touch DNA and how we can use it to inform activity level propositions.

Laura: Excellent, Ray?

Ray: Hey, my name is Ray Wickenheiser. I am a recovering, recently retired forensic scientist. So once a forensic scientist, always a forensic scientist. So, I started right out of university, went back to school a couple of times, moved from lab to lab, but was originally a trace evidence scientist in hair and fiber section. And then when DNA came along, just got really fortunate with stumbling onto that we could get profiles from DNA that was transferred by hand contact or by people touching things as opposed to blood, semen, saliva, that kind of thing. So really for me, it was being able to apply the trace evidence principles to DNA. And it has just become really topical recently that, you know, it’s not just now how the DNA like, whose is the DNA. It’s how did it get there? That is becoming more and more important. So, I think the timing is great, but I’ve been now, and I shudder to say it’s been over 40 years I’ve been doing this, but to be able to apply those same principles I find is very exciting.

Laura: I think it’s very exciting. And what you’re both doing, touch DNA is extremely hot. I mean, everybody wants to know more about it, not just in the community, but in the media as well. Ashley, maybe you can tell us a little bit about activity level propositions and how important they are when you’re thinking about touch DNA evidence.

Ashley: Technology now is so sensitive that many times you can’t reasonably dispute whose DNA it is. So, the real question becomes how did it get there? A simple example I like to use is this. So, say your DNA was found on the knife handle of a knife at a death scene. Right? So, the prosecution is going to say she was there. She did it. See, here’s her DNA. Your defense lawyer is going to say no, no, no. She had lunch with the person who did it. They shook hands, and that person transferred her DNA to the knife. So, your DNA is there. There’s no question about it. What we need to figure out is how it got there.

Laura: So that’s fascinating. I mean, that opens up so many possibilities on both sides.  Ray, your research addresses the difference between primary and secondary DNA transfer. So, let’s talk about that and how significant that distinction is in the real world when you have a case.

Ray: It is very significant. So clearly when you have direct contact that would be in, using Ashley’s example, we have homicide. We have a weapon there and we know who’s DNA it is. And now the idea of how it got there. So clearly in the case of you found DNA on a knife handle and it matches the suspect, one side is going to say, well, it was through direct contact. That’s how it got there. But clearly DNA transfers because it transferred from a hand to a knife. Well, could it transfer to another substrate and that’s how it then transferred over to the knife? So, what we need is data. We’re scientists. Can we generate some data to help inform? Now we also have some common sense to go, well, every time we transfer something, you get a little less transfer. So, the direct is very likely going to be the better explanation. Maybe intuitively, but not only do we have common sense and intuition, we have the ability to apply data. So, you can really apply both. And also, part of it is we have so many different types of crime scenes, and every crime scene is unique. So, you have to be able to apply the judgment, but it always is better informed with better data. So, we want to do both: use some common sense and our experience, knowledge, education, but also supplement that with really good scientific, rigorous data.

Laura: Absolutely. And that that must be tough as this emerges. You know, you’re documenting where that judgment comes in and then where it moves to the data.

Ray: Exactly. Well, for the scientists, it also helps them have confidence when you have data that backs up, “well, I think this is the way it should be. And that’s maybe my opinion. Oh my goodness. My opinion is actually backed up with some good data.” But also recognizing there are few absolutes because depending on the scenario, and we know that many of these are highly variable, but it still can be guided with good data. And sometimes it’s okay to say, “well, I don’t know for sure, but here’s what I think is more likely than something else.”

Laura: Absolutely. Well, along those lines, Ashley, maybe you can talk about the variability and DNA content from person to person. And I know we were talking, I think you’re talking in your presentation, about domesticated fingerprint and domesticated hand methods..

Ashley: So that is one of the biggest problems when you’re dealing with touch and trace level DNA is that it is very, very, variable between people and within people. So, it’s affected by a number of factors. Like when you washed your hands last, the temperature, the environment, what you’ve touched. So even the same person can deposit different amounts of DNA during the day. So, the issue from a research standpoint is we don’t know how much DNA was deposited. So, it makes it difficult to do any quantitative analysis of DNA transfer when you don’t know what you started with. So, we developed the domesticated fingerprint, which is simply a known quantity of DNA in a background of sebaceous fingerprint chemistry. And the domesticated hand is a nitrile glove with an epidermal skin equivalent or mock skin on top of it that we can use to do transfers. And what it does is take out those variabilities from the experiment so we can then focus on DNA transfer, DNA recovery, the things that we’re really looking for.

Laura: That’s fascinating. So, these are really innovative tools. Maybe you can talk about how they were developed and how you’re using them to advance what you’re doing.

Ashley: So the domesticated fingerprint we developed first. At first we were looking to develop a positive control for touch DNA so that you could analyze it along your touch DNA samples and know that you’ve gotten recovery and such. It seems so easy. We know you need a known quantity of DNA. Just put it in some fingerprint chemistry. There’s some great research out there that gives us the recipe for fingerprint chemistry. So, the problem became finding the DNA source. Now we know that an epithelial cell contains six picograms of DNA. So, if we could put a known quantity of epithelial cells into our chemistry, then we know how much DNA we’ve put in. So, we first had to find the cells to use. We thought about Palmer scrapings since those are the real cells that are involved, but we just couldn’t get enough for our experiments. We looked at white blood cells, but they’re these nice, round, healthy things. They do not have the morphology and behavior of the skin we would find. So finally, we landed on buccal cells. They are similar in morphology. Your buccal cells and the cells on your skin are both squamous epithelial cells. The cells on your skin are keratinized, which means that they become filled with a protein called keratin. It serves as a barrier between the outside and inside. Your buccal cells are the same type of cells, but they don’t contain protein, and they have their nucleus, which is where the DNA is. So now we have our cell.

Now we just have to count them. No big deal right? Okay. They like each other. They like to stick together. And you can’t count cells if they’re clumped. And we have to be able to count the number of cells singly to put them into our fingerprint, so there was a little bit of hair pulling. There was a little bit of work. Ultimately, what came out is there is this reagent called aquamacs. It’s used in cell culture, it’s a cell dissociation medium. We couldn’t use it as the manufacturer recommended, because what we’re doing is kind of weird. So, we developed a protocol and we unclamped the cells. So now we can count the cells, we do a buccal scraping, we float the cells off in Aquamacs, we have a procedure to do count the cells. And now we’ve got calculated cells per microliter. Now we know how much we’re adding to our mock fingerprint. Add it to the fingerprint chemistry, bring it up to 20 microliters in PBS and then we can start to deposit it. So now we’ve got a mock fingerprint, our domesticated fingerprint. Right? The cousin of the wild fingerprint that’s deposited naturally in the wild. So, we can now do things like see how much of it stays on the surface, calculate recovery on different surfaces.

But now as we’re thinking of moving into activity level, we have to start doing activities. And pipetting onto a surface isn’t a real activity. So that’s where the domesticated hand was born, because there has to be human contact in a transfer pathway. And I can tell you this one. I swear I lost hair over this one. This one I came to me during the pandemic. I was at home. I was in Chicago, so we were locked down. So, I was working from home, and I was sitting at my table, and I was writing madly all these schemes for how I’m going to transfer a mock fingerprint on a hand. Right? But if I do it on a real hand, that person contributes their DNA. So, I can’t do that. But I want the motion of a handshake. I want the warmth of a hand. I want the friction. I want the pressure. And sometimes I come up with really crazy ideas because I’m a researcher and I get to. And it just popped in my head. What if I made mock skin? And I said, “Oh, well, has anybody done this?” And I went to the literature, and I found that, yes, somebody stole my idea 20 years ago. So, as they often do.

Laura: I hate when that happens. It’s the worst. Right?

Ashley: Wonderful idea. And you find out somebody already did it, but, it just tells you you’re on the right path. There are so many formulations for mock skin for doing different things. So epidermal skin, skin equivalent. I just call it mock skin, because it’s easier. So, we picked three to test. Two of them were formulations that we made in the lab. And then one of them is called lorica leather. We buy it from a company in Germany. We fashioned it onto a nitrile glove. The best way to get it on is Gorilla Glue. And so, we put the skin on the hand. We can now put the mock fingerprint onto the skin and transfer it, or we can put it on a surface and transfer it that way. And in this manner, we can run the pathways, and we can start with a known quantity of DNA. We can watch how it transfers across the pathway under different conditions. We can compare different variables along the way, like how many surfaces are involved. And we can quantify the whole thing. So, we have an actual number to apply. And we run enough replicates that we have significance, we can run statistics on it and convince ourselves that we’re getting the right answer.

Laura: That is a fascinating process that you went through. And I love how you bring in things that make it easy for anybody to understand. And the fact that you’re using Gorilla Glue, that’s hysterical. I mean, that really adds just a nice little touch to it, too. So, yeah, you made good use of your pandemic time, I would say.

Ashley: Oh, but then then I told you I get to do crazy things because I’m in research. Right? And sometimes I go down a pathway where it has absolutely no relevance to an operational lab. Right? And that’s when I call Ray. He’s sort the voice of reason, and he’s the person who has the experience and can he can actually see immediately when things are going to translate well. So that’s why this partnership is so important.

Laura: Well, you’re leading right into my next question because you are working on the proof of concept. You know, how is this going to translate in the real world? And you spoke about a case Idaho versus Kohlberg. Let’s talk about that.

Ray: So certainly, it’s always innocent until proven guilty. So that’s before the courts right now. But we can look at and the whole goal, especially for forensic science research, you want something that has practical application. So certainly, the philosophy of science. You’ve heard it. Fantastic. How we got to taking the variables out and starting with a known amount of DNA of something that is highly variable, but it has to have an application to real world cases. And so, the excitement for me is, well, these are just different substrates. And so, when you have a different substrate. And so, we were thinking subway poles, how might DNA get there by some other means? And then here comes a case where the very important item is a snap on a knife sheath. So, it’s an area of focused contact. Very, very likely whoever (and that’s common sense), is using that knife had to unsnap the sheath. And so, whoever’s DNA is on there, particularly because it was found under one of the bodies, on top of the bed, but still under a body, clearly kind of a smoking gun kind of item. But now you have a substrate. Now, the fact that you’ve worked and created all of this foundation is really just inserting a different kind of object, a different kind of substrate. So now you have that real world application that makes this really, not only a lot of fun, but it makes it so that you’re really going to be able to apply it to some exact case examples.

Laura: That’s remarkable. Maybe we can even delve into that a little bit more. We were going to talk about withstanding scrutiny in a courtroom. So maybe you can talk about cases that have already happened or where you foresee this being used and how you will be able to withstand that criticism when you’ve got the right science behind what you’re doing.

Ray: So, certainly one of the big foremost things is transparency. You know, here’s how the things were done. Here was the scientific rigor so that anyone else can look at what you’ve done, and they can repeat the experiments. And to me, that’s the beauty of science is that transparency and transportability and something that when they see what you’ve done, and they can see that you have also enough replicates (and there’s still going to be some variation), but when you can see the same kind of results reoccurring on an experiment that’s designed well, but also is something where you can transport it and go, well, here’s one where you had a snap, or here you have a subway pole where somebody is saying instead of going directly to the knife, I happen to handle a subway pole. And then someone else, the real killer, came and touched that same spot, and then they took my DNA to the scene. You can reasonably replicate it, so it’s really going to add information that’s objective, that anyone can criticize, or they can look at it and go, that was really done well. And you can now use that to help inform what actually did happen, because we were none of us were at the crime scene other than perhaps that one person who was suspected or committed it. But we really have to provide something that’s really going to inform it with a real-world kind of example and applicability.

Laura: Well, along those lines, I’m sure with anything new, there’s controversy. There’s ethical considerations. Was this primary? Was this tertiary? I mean, not just in implicating someone in the crime, but exonerating them as well. Maybe you can talk a little bit about that controversy and what you see is going to happen.

Ray: That’s a wonderful point. I mean, when you consider again, as forensic scientist, you are neither for the prosecution or for the defense. You’re just for providing best information to the finder of fact. And typically, that’s the jury. So, they’re the ones that have to take all that complex information, apply it to this crime scene, and then they’re making the decision. So, our duty is to give them the best information. But that includes having an opinion. But that opinion can also be even a better opinion based on data. So, if you can provide some data so they can say, well, it looks like in this case direct transfer is a better explanation. But I also have rigorous studies that helped me base that opinion. And here’s why I think that is. And here’s this. Or here’s a secondary transfer scenario that’s very realistic in this situation. So, you really have to take this into consideration. So, we really have a duty to justice to both sides. We have to be neutral. But how do you stay neutral? Here’s my opinion and why, and it’s based on this data that anyone else can replicate. And we’re sharing that data.

Laura: Well yeah. You’re exactly touching on where I was going to go next. I mean, you know, how do you balance those ethical considerations with the scientific data? You touched on a lot of points, but I’d love to actually hear, maybe from both of you, what you think this is going to look like potentially going forward. I mean, we’re guessing a bit, but that’s a that’s okay. This is just the start.

Ashley: Transparency is so important. So, we will of course make all of the data, all of the raw data readily available. We are developing our bullpen of events. This is our repository for all of our information. We put in there our recovery and loss data for a particular surface. We’ve got recovery and loss defined as independent events. So, the idea is we have a repository that maybe it’ll have the knife sheath collected by a cotton swab extracted with DNA IQ. And we have the numbers for each of those. So, you can go into the bullpen and pick your scenario and string it together. And ideally, we hope to grow it large enough that we have information about many, many different scenarios that’s going to be immediately useful, but this is readily available to the public. It’s not secret. The data is freely available. We plan to publish. This research was funded by an NIJ grant. Our final reports will be made public, and it will contain all of the data. And we’ll also deposit our data in a repository.

Ray: So just to add to what Ashley is saying. So, we’re also designing experiments that really have the best scenario for the maximum amount of secondary work for transfer. So, for example I’m using one of the examples is a subway car pole where somebody would put their hand. Now we’re cleaning that off so you can put on the DNA, you know, in a scientific manner. I would venture to guess that probably that subway poll has not been clean except for one point in its lifetime, which when it was brand new. So, there’s probably an incredible mixture of DNA that you could never figure out in reality. But that’s part of the you’re giving under the best, worst case examples that you can possibly set up or experimental examples. Here’s a clean subway pole. Here is now a deposit that’s going on to that. And now somebody coming along right afterwards touching exactly the same spot and then transferring it to the knife handle. Another event and what transfers there? In reality, when you think about how many things that would have to happen. Really? A clean subway pole, is that going to happen? And so, somebody would have to touch exactly that same spot, and then they would commit the murder.

And then here’s what the data would show. So, if you buy those premises but here’s the data that my goodness that is possible. Or for that matter, it’s far less likely than just that person directly touched the knife. But to be able to set up those experiments and have, as Ashley had referred, the bullpen of events, you know, and just like mock fingerprints, you have a lot of fun. And Ashley is extremely creative in coming up with these names. But the idea that you can take different scenarios, and you can have data to go, oh no, it wasn’t a pole, it was a snap. No, it wasn’t a snap. It was a different substrate to be able to put together, just different independent events so they can be put together and you know the data in each one. And you can essentially come up with a formula to go under your circumstance. Here’s what we would expect to see. And that would inform an opinion to be able to just again, give good data to the people who have to make the decision, the jury, so they can make the best decision for each case.

Laura: I mean, I think it’s fascinating, and I love the way that you have used terms that make it easy. Domesticated versus wild. The bullpen. So, just the transparency of the database and the data so people can begin to understand this with any newer technology or where things are being worked through. So that’s an amazing way to push it forward.

Ray: Well, it’s interesting that you’d say like newer technology and the remarkable developments. To me, it’s like a miracle in a tube. What can be done with DNA and so sensitive. But ironically, the same philosophies of trace evidence still apply from hair and fiber days. But instead of fiber floating or being transferred with contact, now it’s DNA, which is much more discriminating. But there’s still how did it get there? And at the end of the day, we’re about what is the truth and what actually occurred? And there’s absolutely situations where I was there innocently, you know, there’s a reason for my DNA to be there, and that information should be as accurately portrayed as possible. So, the finder of fact, the jury can come up with the right decision. And we know secondary transfer occurs. We know that there are parameters and there are situations where it very well likely could be the case as well.

Laura: It’s so interesting. Have you been getting a lot of questions from people after, you know, talking about this with the community here at ISHI?

Ashley: Yeah, and here we’ve mostly gotten… Well, I’ve mostly gotten a good reception. People seem to be very interested in the bullpen and the capability of stringing together a crime scene, giving actual information about what’s happened.

Ray: Yeah, I agree. And it’s such a great group because they’re absolutely about getting the right answer. And what I found really emotional is hearing stories of people who were exonerated because data came to light, evidence, hard evidence that they could not have committed the crime. And the applause and the cheering, the emotion you got was the same or even heightened than when a cold case was solved. People, forensic scientists, are about getting the right answer, and that absolutely includes exonerations. But better data helps us provide the finder of fact with better information because they’ve got a tough job. But the better we can be at it just means we all want to get the right answer. The last thing we want to do is have the wrong person held responsible for a crime that they did not commit. You want the right person, but they’re going to do a better job with better data. And that’s our aim is to provide that just to make it clear and help inform our forensic scientists that they can have well informed opinions to, again, help the finder of fact.

Laura: Well, what fascinating research. And what a fascinating way to push this forward. I mean, if we think back even a decade, it’s unbelievable where we’ve come and it looks like we’re just pushing forward yet again. So, before we let you go, first of all, is there anything we’ve missed that you really want to be sure we include in the video?

Ashley: Well, I don’t think in talking about the research, we’ve developed this domesticated fingerprint. During development, we also run wild fingerprints so we can watch how they compare to each other to make sure that the domesticated fingerprint is a good control. And we have found it is. Like Ray said, it is the best possible scenario. And when we’re talking about subway pole, we have an actual New York City subway pole, so it’s the real thing. It is cleaner than it’s ever been before.

Laura: How did you get it that way? Just curious.

Ashley: It’s ethanol and sterile water. That’s one of the things my students have to troubleshoot for each surface is how we decon it. So, before we do every experiment, we take a background swab. So, we’re absolutely sure that the surface is clean because we’re dealing with such low levels of DNA that we have to know there’s no prior contribution for these experiments.

Ray: Yeah. So, what I’d love to add is I really have treasured the partnership. And so, part of it is Ashley is outstanding to work with and it’s a lot of fun. And so, we really enjoy it. Not just the brainstorming and working together but coming up with something that’s real world applicability. The other piece of it, which I think is outstanding, is the students really embrace it. They’ve got to work on something in order to get their master’s or whichever degree they’re working on, but to able to do something that has real world applicability. But it also really helps in terms of their training, their critical thinking, their thought process, and then for them to then get a job and be able to apply that almost immediately in their training, and then them becoming even better forensic scientists. I think it’s a wonderful partnership to have better students certainly means more meaningful research. And then sort of selfishly, for us in the crime lab, better data that we can have better forensic scientists, better representing and doing what we’re doing, going out to the courts, educating and having better informed opinions. I think it’s a wonderful partnership. And not only is it more fun, but we all benefit a lot from having that collaborative effort.

Laura: And we really appreciate you doing these videos because it goes out to a larger audience, not just the people that are interested in coming potentially to ISHI, but anybody who is interested in forensic science and wants to watch this, and I really appreciate you making it understandable and sharing the new knowledge and training the next generation and not just in new technologies, but like you said, in a way to reason through what they’re doing. That’s fabulous.

Ray: Well, thanks so much for having us. It’s wonderful to be able to share this out.

Laura: It is really appreciated that you’re here. Now, Ray, I know you’ve been with us many times. Ashley, I’m always in the studio, so I never know if people have visited multiple times. This is the first time. How about for you?

Ashley: Yeah, I’ve been here a number of times before. This is my first time speaking at ISHI. I’ve never been on the stage before.

Laura: Okay, since you’ve both been here and it’s our 35th anniversary, we’d love to ask, you know, what have your experiences been like and what brings you back?

Ashley: Well, I like it because of the community. The DNA community is here. I like the talks. The talks are very high level and in the past few ISHI’s they’ve been starting with keynote speakers that are real world and I really enjoy that. It helps me remember why we do what we do.

Laura: It’s wonderful. I really appreciate hearing that. How about you, Ray?

Ray: Yeah. So, for me, getting together with the community and we kind of think of like, what’s our mission in the crime lab and forensic science, we don’t come up with the technology. But we go out, we get together, we sort of shop the world for the best technology and bring it home to our jurisdiction and apply it to our cases. And getting together and seeing and hearing of the successes, as well as the learning experiences from other crime labs. Not only is it fun, but we get to hear what they’re doing and then take that learning and those relationships and bring them back. It just makes our cases better, and at the same time, it’s extremely rejuvenating. We all need to get our batteries charged and as Ashley said, keeping us grounded to know why we do what we do. Hearing from real world people, you know, victims, families, exonerated people that has really impacted. And frankly, hearing these stories, I get the same emotion hearing them virtually. It’s like it’s for the first time even though we come multiple years. But it’s really why we come back.

Laura: Well, thank you both for sharing that. And thank you so much for taking time out with us. We really, really appreciate you being here, not just to share your experience with the panel, but also taking time during the video. Thank you. My pleasure.

Ray: Thanks for having us.