WEBVTT 1 00:00:00.150 --> 00:00:04.209 So back in the summer of 2011, investigators in Michigan 2 00:00:04.240 --> 00:00:07.519 were facing this just absolute geographical nightmare. 3 00:00:07.719 --> 00:00:09.140 Oh, the Baby Kate case. 4 00:00:09.320 --> 00:00:12.439 Right, yeah. This young child, who the media ended up 5 00:00:12.480 --> 00:00:15.859 calling Baby Kate, had tragically gone missing. And the suspect, 6 00:00:16.760 --> 00:00:21.250 her father, gave police this incredibly vague account of where 7 00:00:21.289 --> 00:00:24.929 he had been that day. So based on his timeline 8 00:00:25.170 --> 00:00:28.620 and his vehicle... the search grid ballooned to cover like 9 00:00:28.739 --> 00:00:29.739 seven different counties. 10 00:00:29.780 --> 00:00:31.399 Which is just a massive area. 11 00:00:31.480 --> 00:00:34.100 It's impossible. I mean, searching seven counties for a single 12 00:00:34.479 --> 00:00:37.579 hidden location is like looking for a needle in a haystack, 13 00:00:37.659 --> 00:00:39.340 if the haystack was the size of a mountain range. 14 00:00:39.439 --> 00:00:39.659 Right. 15 00:00:39.939 --> 00:00:42.179 But the investigators, they have the suspect's shoes. 16 00:00:42.479 --> 00:00:45.560 And those shoes were covered in a very fine, seemingly 17 00:00:45.619 --> 00:00:47.840 inconsequential layer of dirt and plant matter. 18 00:00:47.899 --> 00:00:50.200 Yeah, which is where a botanist named Matt Von Conrad 19 00:00:50.219 --> 00:00:52.619 stepped in. Because he didn't just look at the shoes 20 00:00:52.659 --> 00:00:55.210 and see mud. He put the debris under a microscope. 21 00:00:55.619 --> 00:00:59.109 and found a highly specific combination of moss fragments. And 22 00:00:59.170 --> 00:01:03.890 because moss is incredibly picky about its environment, requiring very 23 00:01:03.929 --> 00:01:08.390 specific levels of shade and moisture and soil acidity, that 24 00:01:08.469 --> 00:01:12.659 combination of microscopic plants served as essentially a GPS coordinate. 25 00:01:12.959 --> 00:01:13.980 It's amazing. 26 00:01:14.219 --> 00:01:17.620 It took a search grid of seven counties, this impossibly 27 00:01:17.680 --> 00:01:20.099 vast expanse of land, and shrank it down to a 28 00:01:20.120 --> 00:01:22.200 microhabitat measured in tens of square feet. 29 00:01:22.299 --> 00:01:22.739 Wow. 30 00:01:23.129 --> 00:01:25.069 So today we are diving into a stack of research 31 00:01:25.090 --> 00:01:27.930 and case files on something called forensic botany. 32 00:01:28.129 --> 00:01:28.409 Right. 33 00:01:28.709 --> 00:01:32.189 It's a practice of treating plants, twigs, seeds, pollen, and 34 00:01:32.230 --> 00:01:36.319 moss as physical evidence in criminal investigations. And our mission 35 00:01:36.340 --> 00:01:39.780 today is to explore how nature's quietest organisms keep a 36 00:01:39.840 --> 00:01:43.379 stubborn record of human actions. Yep. especially when human witnesses 37 00:01:43.480 --> 00:01:44.659 lie or disappear. 38 00:01:44.920 --> 00:01:47.939 It is a remarkable field, but we should probably establish 39 00:01:47.980 --> 00:01:49.120 a baseline right away. 40 00:01:49.170 --> 00:01:49.329 Sure. 41 00:01:49.500 --> 00:01:52.250 Plants are not magical oracles. We aren't talking about some 42 00:01:52.290 --> 00:01:53.670 mystical connection to the forest. 43 00:01:53.709 --> 00:01:54.109 Right, right. 44 00:01:54.250 --> 00:01:57.810 Plants are physical evidence, and they're governed by strict ecological rules. 45 00:01:58.409 --> 00:02:02.390 They have biological schedules. They are restricted to specific growing ranges, 46 00:02:02.909 --> 00:02:04.909 and they carry unique genetic fingerprints. 47 00:02:05.370 --> 00:02:08.969 Okay, let's unpack this, because it sounds almost like a superpower. 48 00:02:09.439 --> 00:02:12.289 But it is deeply grounded in biology. Exactly. 49 00:02:12.669 --> 00:02:14.750 When we look at a crime scene in a forest 50 00:02:14.849 --> 00:02:17.969 or a field, the expectation is that the crime is 51 00:02:18.030 --> 00:02:21.949 simply unwitnessed. But if you can read the ecology, you 52 00:02:21.990 --> 00:02:24.889 realize the environment itself is documenting the event. 53 00:02:25.750 --> 00:02:28.120 Before we get into the molecular genetics and the high-tech 54 00:02:28.129 --> 00:02:30.759 side of this, I want the listener to try something. 55 00:02:31.840 --> 00:02:34.699 Look down at your shoes right now. Or think about 56 00:02:34.740 --> 00:02:36.560 the jacket you wore the last time you went for 57 00:02:36.580 --> 00:02:37.460 a walk outside. 58 00:02:37.479 --> 00:02:37.780 Mm-hmm. 59 00:02:38.460 --> 00:02:43.150 What microscopic evidence are you unknowingly carrying with you? Because 60 00:02:43.169 --> 00:02:44.069 you are carrying something. 61 00:02:44.409 --> 00:02:47.409 You absolutely are. I mean, every single time you step outside, 62 00:02:47.449 --> 00:02:50.490 you are moving through the bulk of Earth's living biomass. 63 00:02:50.949 --> 00:02:54.710 You're brushing against pollen, picking up spores, crushing leaves, and 64 00:02:54.770 --> 00:02:57.870 transferring organic material from the landscape straight to your clothing, 65 00:02:57.930 --> 00:02:59.030 your hair, and your vehicle. 66 00:02:59.189 --> 00:02:59.810 It's everywhere. 67 00:02:59.870 --> 00:03:02.219 The environment is constantly rubbing off on you. 68 00:03:02.520 --> 00:03:04.300 I'm trying to visualize how we even got to the 69 00:03:04.360 --> 00:03:06.599 point where a court of law would accept this, though. 70 00:03:07.669 --> 00:03:10.250 You don't just walk into a courtroom with a microscopic 71 00:03:10.289 --> 00:03:12.009 piece of moss and point at a suspect. 72 00:03:12.210 --> 00:03:12.449 No. 73 00:03:12.650 --> 00:03:16.159 There has to be a foundation, like a precedent for 74 00:03:16.240 --> 00:03:17.659 treating nature as a witness. 75 00:03:18.199 --> 00:03:21.360 You need an incredibly strong precedent. And the foundation for 76 00:03:21.400 --> 00:03:24.789 forensic botany in the courtroom doesn't begin with a microscope 77 00:03:24.830 --> 00:03:26.759 and a leaf. It begins with a ladder. 78 00:03:26.780 --> 00:03:27.479 Oh, wow. 79 00:03:27.780 --> 00:03:32.860 Specifically in what was arguably the most famous criminal investigation 80 00:03:32.900 --> 00:03:33.900 in American history. 81 00:03:34.159 --> 00:03:36.810 Oh, the 1932 Lindbergh baby kidnapping. 82 00:03:36.930 --> 00:03:37.620 That's the one. 83 00:03:37.789 --> 00:03:40.069 This was the quote unquote trial of the century. I mean, 84 00:03:40.090 --> 00:03:44.449 Charles Lindbergh was an international hero for his solo transatlantic flight. 85 00:03:44.610 --> 00:03:44.930 Yeah. 86 00:03:45.409 --> 00:03:47.289 So when his 20 month old son was taken from 87 00:03:47.330 --> 00:03:50.710 his nursery in Hopewell, New Jersey, the entire country just 88 00:03:50.810 --> 00:03:51.729 came to a standstill. 89 00:03:51.849 --> 00:03:52.770 It was a massive deal. 90 00:03:53.169 --> 00:03:55.500 It was a tragedy that ended with the child found dead. 91 00:03:56.030 --> 00:03:59.530 But the kidnapper made a critical mistake. They left a 92 00:03:59.569 --> 00:04:01.550 homemade wooden ladder behind at the scene. 93 00:04:01.849 --> 00:04:04.729 And that homemade ladder became the most scrutinized piece of 94 00:04:04.789 --> 00:04:08.150 physical evidence in the world at that time. Wow. And 95 00:04:08.189 --> 00:04:11.509 that's where Arthur Kohler enters the picture. Kohler was a 96 00:04:11.590 --> 00:04:15.270 wood identification expert at the United States Forest Products Laboratory 97 00:04:15.349 --> 00:04:16.470 in Madison, Wisconsin. 98 00:04:16.980 --> 00:04:18.620 I have to pause on that because it's such an 99 00:04:18.709 --> 00:04:22.800 interesting historical detail. He wasn't a police scientist. No. He 100 00:04:22.839 --> 00:04:23.720 wasn't a detective. 101 00:04:23.980 --> 00:04:28.279 Not at all. Kohler spent his days answering industrial questions 102 00:04:28.319 --> 00:04:32.300 for lumber yards and builders. He studied wood grain, milling marks, 103 00:04:32.519 --> 00:04:35.879 and how different species of boards shrank and swelled based 104 00:04:35.939 --> 00:04:39.879 on ambient moisture. So when federal investigators brought him the 105 00:04:39.920 --> 00:04:45.459 Lindbergh Ladder, he approached it with a purely industrial anatomical methodology. 106 00:04:45.839 --> 00:04:47.850 So he just stripped away the context of the murder 107 00:04:47.870 --> 00:04:49.189 and looked at the biology of the wood. 108 00:04:49.439 --> 00:04:53.170 Exactly. He first identified the species used to construct the ladder, 109 00:04:53.230 --> 00:04:57.740 which were Douglas fir, ponderosa pine, and birch. Because softwoods 110 00:04:57.779 --> 00:05:02.370 and hardwoods have fundamentally different cellular structures, hardwoods like birch 111 00:05:02.449 --> 00:05:06.629 contain specialized cells called vessels for transporting water, which look 112 00:05:06.649 --> 00:05:08.629 like tiny pores under magnification. 113 00:05:08.949 --> 00:05:09.949 Oh, I see. Right? 114 00:05:10.089 --> 00:05:13.470 And softwoods like pine lack these vessels and rely on 115 00:05:13.490 --> 00:05:17.060 a different cell type called trachyids. So Kohler could easily 116 00:05:17.139 --> 00:05:18.060 prove the species. 117 00:05:18.319 --> 00:05:20.420 But knowing the latter was made of pine doesn't catch 118 00:05:20.439 --> 00:05:23.079 a kidnapper. Millions of things are made of pine. 119 00:05:23.120 --> 00:05:26.389 Right, exactly. Exactly. The breakthrough in the sources comes when 120 00:05:26.410 --> 00:05:30.209 he narrows his focus to one specific rail of the ladder. 121 00:05:30.230 --> 00:05:30.629 Okay. 122 00:05:30.910 --> 00:05:33.920 Because a piece of pine is not just a generic material. 123 00:05:34.300 --> 00:05:37.160 It grew in a specific place during specific weather conditions. 124 00:05:37.339 --> 00:05:37.740 Oh, right. 125 00:05:38.259 --> 00:05:42.420 Kohler studied the individual rail and noticed two crucial things. First, 126 00:05:42.540 --> 00:05:45.199 it had four very distinctive square nail holes. 127 00:05:45.439 --> 00:05:45.600 Okay. 128 00:05:45.990 --> 00:05:48.029 Second, the pattern of the annual winds, you know, the 129 00:05:48.050 --> 00:05:50.110 concentric circles you see when you cut a tree down. 130 00:05:50.269 --> 00:05:50.430 Yeah. 131 00:05:50.860 --> 00:05:53.720 That indicated that this specific rail hadn't just been milled 132 00:05:53.759 --> 00:05:56.759 directly from a log. The curvature and spacing of the 133 00:05:56.819 --> 00:05:58.800 ring showed that it had been sawn off from a 134 00:05:58.879 --> 00:06:00.579 much wider pre-existing board. 135 00:06:00.980 --> 00:06:04.040 I love the mechanics of this. So Kohler maps out 136 00:06:04.079 --> 00:06:07.430 the physical geometry of this wood. He tracks the milling 137 00:06:07.449 --> 00:06:12.370 marks to specific machines and specific lumber yards. And eventually, 138 00:06:12.430 --> 00:06:15.370 the investigation leads police to the Bronx apartment of a 139 00:06:15.449 --> 00:06:17.649 carpenter named Bruno Richard Hauptman. 140 00:06:17.910 --> 00:06:18.410 Right. 141 00:06:18.850 --> 00:06:21.040 They search his home. They go up into his attic 142 00:06:21.379 --> 00:06:24.360 and they find a floorboard with a large section missing. 143 00:06:24.600 --> 00:06:27.379 And this is where the analog methodology just reaches its peak. 144 00:06:27.620 --> 00:06:29.980 Kohler takes the ladder rail from the crime scene and 145 00:06:30.019 --> 00:06:33.300 the damaged floorboard from Hopman's attic and places them side 146 00:06:33.339 --> 00:06:33.819 by side. 147 00:06:34.040 --> 00:06:34.319 Wow. 148 00:06:34.740 --> 00:06:37.740 The pattern of the annual tree rings flowed perfectly from 149 00:06:37.759 --> 00:06:39.680 the attic board into the ladder rail. 150 00:06:40.019 --> 00:06:40.560 No way. 151 00:06:40.839 --> 00:06:43.879 Yeah. And furthermore, the four square nail holes in the 152 00:06:43.920 --> 00:06:46.540 ladder rail aligned exactly with the floor joists in the 153 00:06:46.660 --> 00:06:48.660 attic where the original board had been nailed down. 154 00:06:49.069 --> 00:06:51.879 So a piece of wood is essentially a jigsaw puzzle 155 00:06:51.920 --> 00:06:55.120 piece with a biological barcode printed on the side. 156 00:06:55.339 --> 00:06:57.519 That is a brilliant way to frame it. Tree wings 157 00:06:57.660 --> 00:07:01.139 are entirely dictated by the environment. A year with heavy 158 00:07:01.199 --> 00:07:05.170 rainfall produces a wide, thick ring because the tree grew rapidly. 159 00:07:05.189 --> 00:07:09.910 A drought year produces a narrow, dense ring. That sequence 160 00:07:09.970 --> 00:07:12.990 of wide and narrow bands becomes a permanent barcode of 161 00:07:13.029 --> 00:07:15.420 the weather that specific tree experienced. 162 00:07:15.670 --> 00:07:16.370 That's crazy. 163 00:07:16.430 --> 00:07:18.370 The wood in the attic and the wood at the 164 00:07:18.430 --> 00:07:23.290 crime scene shared the exact same barcode. They were undeniably 165 00:07:23.449 --> 00:07:24.810 once a single plank. 166 00:07:25.110 --> 00:07:27.730 But I'm imagining the defense attorneys at the time, this 167 00:07:27.790 --> 00:07:30.350 is 1935 when it goes to trial. Yeah. They must 168 00:07:30.370 --> 00:07:32.750 have fought violently to keep this guy off the stand. 169 00:07:33.410 --> 00:07:37.029 Oh, they fought tooth and nail. The defense argument was literally, 170 00:07:37.129 --> 00:07:39.949 and I quote, there is no animal known among men 171 00:07:40.209 --> 00:07:41.329 as an expert in wood. 172 00:07:41.529 --> 00:07:41.829 Wow. 173 00:07:42.250 --> 00:07:44.959 Yeah. They tried to frame him as a charlatan because 174 00:07:45.220 --> 00:07:48.920 forensic wood analysis simply wasn't a recognized legal concept. Right. 175 00:07:49.000 --> 00:07:49.639 It was totally new. 176 00:07:49.879 --> 00:07:53.939 But the judge recognized the empirical rigor of Kohler's work 177 00:07:54.060 --> 00:07:57.959 and allowed the testimony. By doing so, that judge permanently 178 00:07:58.079 --> 00:08:01.149 opened the courtroom door for dendrochronology, which is the study 179 00:08:01.170 --> 00:08:03.350 of tree rings and botanical anatomy. 180 00:08:03.550 --> 00:08:06.170 It's an incredible foundation. Just a man with a deep 181 00:08:06.209 --> 00:08:09.589 understanding of cellular structure, tracing the geometry of a tree. 182 00:08:10.129 --> 00:08:12.240 But we're talking about a massive piece of lumber here. Yeah. 183 00:08:12.470 --> 00:08:16.009 A ladder is macroscopic evidence. It makes sense that if 184 00:08:16.029 --> 00:08:17.769 you have a giant plank of wood, you can match 185 00:08:17.810 --> 00:08:18.180 the grain. 186 00:08:18.269 --> 00:08:18.500 Sure. 187 00:08:18.600 --> 00:08:21.560 My question is, how does this transition to the microscopic? 188 00:08:22.279 --> 00:08:24.980 What happens when the evidence isn't a ladder, but just 189 00:08:25.040 --> 00:08:26.339 a single leaf or a seed? 190 00:08:26.560 --> 00:08:29.500 Well, that requires a monumental leap in the science. We 191 00:08:29.540 --> 00:08:32.919 have to move away from visual anatomical matching and dive 192 00:08:32.960 --> 00:08:34.460 into molecular genetics. 193 00:08:34.879 --> 00:08:35.120 Okay. 194 00:08:35.259 --> 00:08:37.980 The case that pushed forensic botany into the genetic age 195 00:08:38.399 --> 00:08:41.409 happened recently. 60 years after the Lindbergh trial in a 196 00:08:41.529 --> 00:08:42.710 vastly different landscape. 197 00:08:42.769 --> 00:08:46.690 So we're looking at 1992 in Maricopa County, Arizona. A 198 00:08:46.730 --> 00:08:48.730 dirt bike rider is out in the desert west of 199 00:08:48.789 --> 00:08:52.250 Phoenix and discovers the body of a woman named Denise 200 00:08:52.289 --> 00:08:56.399 Johnson in a dry wash. It's a desolate area, but 201 00:08:56.480 --> 00:08:58.919 right near where she was found, there's a small cluster 202 00:08:59.019 --> 00:08:59.960 of Palo Verde trees. 203 00:09:00.299 --> 00:09:03.059 And Palo Verdes are incredibly common in the Sonoran Desert. 204 00:09:03.120 --> 00:09:05.980 They have this green bark that can photosynthesize And they 205 00:09:06.009 --> 00:09:08.340 drop these very distinct seed pods. 206 00:09:08.419 --> 00:09:11.240 Right. So investigators process the scene and they find a pager, 207 00:09:11.279 --> 00:09:13.919 which was a big deal in 1992. Oh, yeah. Huge. 208 00:09:14.259 --> 00:09:18.750 And that pager leads them to a suspect named Mark Bogan. Now, 209 00:09:18.809 --> 00:09:22.809 Bogan admits to police that he knew the victim. However, 210 00:09:23.250 --> 00:09:25.889 he is adamant that he was never at that specific 211 00:09:26.210 --> 00:09:29.529 desert dump site. He claims his truck never went anywhere 212 00:09:29.600 --> 00:09:30.269 near that wash. 213 00:09:30.679 --> 00:09:34.019 But the physical scene contradicted him. A detective named Charlie 214 00:09:34.080 --> 00:09:36.480 Norton noticed that one of the Palo Verde trees near 215 00:09:36.519 --> 00:09:40.980 the body, a tree they cataloged as PV-30, had a fresh, 216 00:09:41.299 --> 00:09:42.960 raw scrape on a lower branch. 217 00:09:43.279 --> 00:09:43.500 Okay. 218 00:09:43.620 --> 00:09:46.039 It looked exactly as if a vehicle had driven past 219 00:09:46.100 --> 00:09:47.360 in the brush and clipped the tree. 220 00:09:47.799 --> 00:09:50.990 And when police execute a search warrant on Bogan's pickup truck, 221 00:09:51.409 --> 00:09:53.750 they look in the truck bed and they find two 222 00:09:54.210 --> 00:09:57.570 Palo Verde seed pods. Right. Now, I'm putting myself in 223 00:09:57.590 --> 00:10:00.429 the shoes of a defense attorney here. Finding a seed 224 00:10:00.470 --> 00:10:03.220 pod from a tree that grows all over Arizona inside 225 00:10:03.250 --> 00:10:05.980 a pickup truck in Arizona doesn't seem like a smoking gun. 226 00:10:06.279 --> 00:10:07.980 It feels entirely circumstantial. 227 00:10:08.240 --> 00:10:10.679 And under normal circumstances, it would be. The defense would 228 00:10:10.700 --> 00:10:12.039 just say, you know, a pod fell on his truck 229 00:10:12.059 --> 00:10:13.860 while he was parked at the grocery store. To deep 230 00:10:13.879 --> 00:10:16.919 that defense, Detective Norton asked a question that no one 231 00:10:16.960 --> 00:10:20.250 had ever asked in a U.S. criminal court. He reached 232 00:10:20.330 --> 00:10:22.690 out to a plant geneticist at the University of Arizona 233 00:10:22.730 --> 00:10:24.169 named Timothy Hellant-Jarsis. 234 00:10:24.500 --> 00:10:24.799 Okay. 235 00:10:24.860 --> 00:10:27.379 And he asked, can you prove that these two specific 236 00:10:27.460 --> 00:10:30.419 pods in the truck came from that one specific scraped 237 00:10:30.500 --> 00:10:31.679 tree at the crime scene? 238 00:10:31.980 --> 00:10:35.240 Which is a wild request for 1992. I mean, human 239 00:10:35.279 --> 00:10:40.269 DNA profiling in courts was still relatively new and highly contested. 240 00:10:40.429 --> 00:10:42.330 Asking to profile a bush in the desert is a 241 00:10:42.470 --> 00:10:43.269 huge swing. 242 00:10:43.370 --> 00:10:46.169 It was a massive risk. Hellant-Jarsis decided to employ a 243 00:10:46.210 --> 00:10:48.929 technique that was cutting edge at the time called RAPD. 244 00:10:49.549 --> 00:10:52.649 That stands for randomly amplified polymorphic DNA. 245 00:10:52.710 --> 00:10:55.029 Okay. I think we need an ELI 5 here. Like, 246 00:10:55.210 --> 00:10:59.190 explain it like I'm 5 on RAPD. Because randomly amplified 247 00:10:59.230 --> 00:11:02.570 polymorphic DNA is a mouthful. How does this actually work? 248 00:11:03.090 --> 00:11:05.669 Fair enough. Imagine the DNA of a tree is an 249 00:11:05.740 --> 00:11:07.929 encyclopedia containing millions of sentences. 250 00:11:08.009 --> 00:11:08.240 Okay. 251 00:11:08.460 --> 00:11:11.000 Instead of trying to read the entire encyclopedia from start 252 00:11:11.019 --> 00:11:14.120 to finish, which would take years, RAPD acts like a 253 00:11:14.159 --> 00:11:17.539 search function that looks for a few very specific random sentences. 254 00:11:17.559 --> 00:11:18.100 Ah, I see. 255 00:11:18.429 --> 00:11:20.929 You take the DNA from the seed pod and you 256 00:11:20.970 --> 00:11:23.710 take the DNA from the crime scene tree. You apply 257 00:11:23.750 --> 00:11:26.350 chemicals that search for those random sentences. 258 00:11:26.490 --> 00:11:26.690 Right. 259 00:11:27.330 --> 00:11:30.240 If the pod and the tree both produce the exact 260 00:11:30.299 --> 00:11:33.980 same pattern of sentences and no other tree produces that pattern, 261 00:11:34.399 --> 00:11:35.139 you have a match. 262 00:11:35.519 --> 00:11:38.279 But how do you prove that in court? How do 263 00:11:38.299 --> 00:11:40.480 you prove that another tree down the street wouldn't just 264 00:11:40.539 --> 00:11:43.370 happen to have the same sentences? Ah. This is what 265 00:11:43.379 --> 00:11:46.509 stood out to me in the sources. The absolute rigor... 266 00:11:46.799 --> 00:11:49.919 of the scientific method the police applied to their own scientist. 267 00:11:50.059 --> 00:11:51.110 The blind test. 268 00:11:51.250 --> 00:11:51.519 Yeah. 269 00:11:51.950 --> 00:11:55.049 It is a beautiful piece of investigative work. To ensure 270 00:11:55.110 --> 00:11:58.450 Helen Joris wasn't just finding a generic Palo Verde profile, 271 00:11:58.470 --> 00:12:02.049 the police drove all around Phoenix. They went to Bogan's house, 272 00:12:02.250 --> 00:12:05.860 his workplace, his favorite bars, and they collected seed pods 273 00:12:05.940 --> 00:12:08.000 from 18 random Palo Verde trees. 274 00:12:08.139 --> 00:12:08.440 Wow. 275 00:12:08.559 --> 00:12:10.919 They sent all 18 samples to Helen Joris, but they 276 00:12:11.100 --> 00:12:15.220 also secretly slipped in extra unlabeled material from the crime 277 00:12:15.259 --> 00:12:15.980 scene tree PV30. 278 00:12:16.669 --> 00:12:17.350 Oh, that's smart. 279 00:12:17.429 --> 00:12:18.860 They essentially said, all right, prove it. 280 00:12:19.230 --> 00:12:23.669 And the results are phenomenal. Helen Jaras runs the RAPD analysis. 281 00:12:24.409 --> 00:12:27.720 None of the 18 random trees matched the pods found 282 00:12:27.740 --> 00:12:29.980 in the suspect's truck. Right. But the sample from the 283 00:12:30.019 --> 00:12:33.320 crime scene tree matched. And the secret blind sample the 284 00:12:33.360 --> 00:12:34.659 police slipped in also matched. 285 00:12:34.919 --> 00:12:37.679 If we connect this to the bigger picture, this case 286 00:12:37.740 --> 00:12:40.870 proved that an individual plant, not just a broad species, 287 00:12:40.929 --> 00:12:44.580 but a single living organism... can be a unique source 288 00:12:44.659 --> 00:12:45.639 of trace evidence. 289 00:12:45.799 --> 00:12:46.539 That's incredible. 290 00:12:46.659 --> 00:12:49.860 It established that plant genetics could withstand the exact same 291 00:12:49.960 --> 00:12:54.399 hostile cross-examination and rigorous courtroom standards that are applied to 292 00:12:54.450 --> 00:12:55.149 human DNA. 293 00:12:55.330 --> 00:12:57.190 But wait, I want to clarify a detail about the 294 00:12:57.210 --> 00:13:00.289 biology here, because the success of this case hinged on 295 00:13:00.309 --> 00:13:01.370 the background population. 296 00:13:01.470 --> 00:13:01.830 Yes. 297 00:13:02.210 --> 00:13:05.710 The sources mention that palaverdes in the wild are outbred. 298 00:13:06.009 --> 00:13:09.669 They rely on insects to cross-pollinate them, meaning every seed 299 00:13:09.740 --> 00:13:11.600 is a genetic mix of different parent trees. 300 00:13:11.700 --> 00:13:11.899 Mm-hmm. 301 00:13:12.250 --> 00:13:15.710 They are incredibly genetically noisy. What would happen if this 302 00:13:15.769 --> 00:13:18.029 crime took place in a suburban neighborhood next to a 303 00:13:18.090 --> 00:13:19.110 row of landscape trees? 304 00:13:19.509 --> 00:13:22.990 That is a critical limitation to understand. If a landscaper 305 00:13:23.049 --> 00:13:27.250 plants 20 identical cloned maple trees down a suburban street, 306 00:13:27.809 --> 00:13:31.350 they are all genetically identical. They are grown from cuttings 307 00:13:31.389 --> 00:13:34.519 of a single parent. So if a leaf from one 308 00:13:34.539 --> 00:13:38.399 of those maples falls into a suspect's car, DNA analysis 309 00:13:38.440 --> 00:13:40.580 cannot tell you which of the 20 trees it came from. 310 00:13:41.090 --> 00:13:41.850 Because they're clones. 311 00:13:42.129 --> 00:13:46.490 Exactly. The RAPD technique would show the exact same sentences 312 00:13:46.529 --> 00:13:49.190 for all of them. The match in Arizona was only 313 00:13:49.250 --> 00:13:52.669 powerful because the background population of wild desert trees was 314 00:13:52.750 --> 00:13:53.429 so diverse. 315 00:13:53.529 --> 00:13:54.720 Okay, that makes total sense. 316 00:13:55.029 --> 00:13:58.279 Forensic botanists have to constantly evaluate whether the flora at 317 00:13:58.320 --> 00:14:01.679 a scene is actually informative or practically useless. Right. 318 00:14:01.759 --> 00:14:04.279 If everyone in the room has the exact same fingerprint, 319 00:14:04.559 --> 00:14:06.299 dusting for prints doesn't help you. 320 00:14:06.460 --> 00:14:07.039 Exactly. 321 00:14:07.159 --> 00:14:10.350 So we've established that a single genetically unique tree... can 322 00:14:10.389 --> 00:14:13.820 tether a suspect to a specific location. But this assumes 323 00:14:13.860 --> 00:14:16.460 the police know where the crime scene is. What happens 324 00:14:16.480 --> 00:14:20.539 when investigators have a victim but absolutely no location? If 325 00:14:20.580 --> 00:14:23.080 the landscape is a mystery, how can plants help? 326 00:14:23.440 --> 00:14:25.659 To solve that problem, we have to shrink our scale 327 00:14:25.720 --> 00:14:29.580 even further. We move from the macroscopic ladder past the 328 00:14:29.620 --> 00:14:32.909 seed pod down to something that is biologically engineered to 329 00:14:32.950 --> 00:14:35.590 travel through the air. We are talking about pollen. 330 00:14:36.250 --> 00:14:39.320 I am fascinated by pollen. Because when I think of pollen, 331 00:14:39.399 --> 00:14:41.659 I just think of the yellow dust covering my windshield 332 00:14:41.700 --> 00:14:43.139 in the spring that makes me sneeze. 333 00:14:43.379 --> 00:14:44.720 Yeah, that's most people. 334 00:14:44.980 --> 00:14:48.039 But structurally, it is incredibly resilient. 335 00:14:48.259 --> 00:14:52.169 It is practically indestructible in the natural environment. The outer 336 00:14:52.210 --> 00:14:54.269 wall of a pollen grain is made of a polymer 337 00:14:54.350 --> 00:14:57.190 called sporopollinin. Sporopollinin? 338 00:14:57.230 --> 00:14:57.610 Yes. 339 00:14:58.049 --> 00:15:00.879 You can think of sporopollinin as microscopic Kevlar. 340 00:15:01.320 --> 00:15:01.669 Oh, wow. 341 00:15:01.769 --> 00:15:04.840 It is one of the most durable organic materials on Earth. 342 00:15:05.399 --> 00:15:08.919 It evolved to protect the fragile genetic material inside from 343 00:15:08.950 --> 00:15:13.210 UV radiation, drying out, and physical damage while the pollen 344 00:15:13.269 --> 00:15:15.649 travels on the wind or on the legs of an insect. 345 00:15:15.929 --> 00:15:18.629 And because it's so tough, it acts like a geographical ochre. 346 00:15:19.629 --> 00:15:21.710 I want to look at a deeply tragic case from 347 00:15:21.870 --> 00:15:26.340 June 2015 that perfectly illustrates this. A dog walker on 348 00:15:26.389 --> 00:15:30.539 Boston's Deer Island found a garbage bag containing the remains 349 00:15:30.600 --> 00:15:33.340 of a small girl. She became known in the media 350 00:15:33.460 --> 00:15:34.779 as Boston's Baby Doe. 351 00:15:34.879 --> 00:15:36.139 Right, I remember that. 352 00:15:36.500 --> 00:15:38.799 The police were at a total dead end. She had 353 00:15:38.879 --> 00:15:43.120 no usable fingerprints, generic clothing, and a nationwide composite image 354 00:15:43.419 --> 00:15:47.220 yielded no credible leads. But the investigators decided to look 355 00:15:47.259 --> 00:15:48.039 closer at the scene. 356 00:15:48.539 --> 00:15:53.029 They brought in analysts who essentially vacuumed the child's hair, 357 00:15:53.149 --> 00:15:55.990 her clothing, and a blanket she was found with, specifically 358 00:15:56.049 --> 00:15:57.769 targeting trace botanical evidence. 359 00:15:57.909 --> 00:16:01.929 I'm just picturing crime scene techs vacuuming a toddler's blanket. 360 00:16:01.950 --> 00:16:04.690 It sounds so delicate. But also, what are they actually 361 00:16:04.730 --> 00:16:05.429 hoping to find? 362 00:16:05.629 --> 00:16:06.129 Well. 363 00:16:06.149 --> 00:16:09.110 To the naked eye, they're just collecting dust. How does 364 00:16:09.169 --> 00:16:10.149 dust solve a murder? 365 00:16:10.409 --> 00:16:13.090 Because that dust isn't just dirt. It contains pollen grains 366 00:16:13.149 --> 00:16:15.600 that act as a botanical recipe of the environment the 367 00:16:15.620 --> 00:16:16.320 child had been in. 368 00:16:16.460 --> 00:16:17.000 A recipe. 369 00:16:17.279 --> 00:16:21.759 Forensic botanists call these recipes assemblages. When the analysts looked 370 00:16:21.799 --> 00:16:23.960 at the pollen from the child, they found a mix 371 00:16:24.059 --> 00:16:25.659 dominated by oak and pine. 372 00:16:26.139 --> 00:16:28.000 Which doesn't seem that helpful, right? I mean, oak and 373 00:16:28.039 --> 00:16:31.100 pine cover massive portions of the northeastern United States. 374 00:16:32.220 --> 00:16:35.519 True. But an assemblage is about the combination of elements. 375 00:16:36.220 --> 00:16:39.179 Alongside the common oak and pine, they found pollen from 376 00:16:39.240 --> 00:16:41.120 privet and cedar of Lebanon. 377 00:16:41.500 --> 00:16:44.470 Neither of which are wild native plants you'd find deep 378 00:16:44.490 --> 00:16:46.250 in a New England forest. Exactly. 379 00:16:46.690 --> 00:16:50.009 Privet is a common ornamental hedge. Cedar of Lebanon is 380 00:16:50.049 --> 00:16:52.649 an exotic tree often planted in landscaping. 381 00:16:53.000 --> 00:16:53.519 Oh, interesting. 382 00:16:53.659 --> 00:16:57.039 These are plants you find in residential suburbs, manicured parks, 383 00:16:57.200 --> 00:17:02.149 and domestic yards. Furthermore, the analysts found microscopic soot particles 384 00:17:02.250 --> 00:17:03.490 mixed in with the pollen. 385 00:17:03.929 --> 00:17:04.289 Soot? 386 00:17:04.609 --> 00:17:09.369 Yes, which strongly indicated an urban or highly trafficked environment. 387 00:17:09.670 --> 00:17:12.349 So instead of looking at thousands of square miles of 388 00:17:12.450 --> 00:17:17.650 rural forest or distant states, this microscopic cocktail of pollen 389 00:17:17.690 --> 00:17:21.529 and soot points investigators firmly toward an urban landscaped environment. 390 00:17:21.789 --> 00:17:24.609 It radically shrank the map. It told investigators where not 391 00:17:24.650 --> 00:17:27.369 to look, which saved thousands of hours of wasted effort. 392 00:17:27.569 --> 00:17:27.809 Wow. 393 00:17:27.990 --> 00:17:31.170 Within months, focusing on local urban areas, the child was 394 00:17:31.230 --> 00:17:35.410 identified as Bella Bond, a two-year-old from Dorchester, a residential 395 00:17:35.470 --> 00:17:36.309 Boston neighborhood. 396 00:17:36.349 --> 00:17:36.890 That's incredible. 397 00:17:37.089 --> 00:17:40.029 Pollen is rarely going to give you a specific street address, 398 00:17:40.710 --> 00:17:42.589 but it acts as an ecological constraint. 399 00:17:43.210 --> 00:17:45.519 And because that spore of pollen and armor is so tough, 400 00:17:46.079 --> 00:17:49.440 this ecological constraint can last for staggering amounts of time. 401 00:17:49.559 --> 00:17:50.200