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Blood Trails, DNA, and O. J.
Since 1985, with Alec Jeffrey's discovery of the uniqueness of portions of the DNA structure of certain genes, investigations involving blood have taken an entirely new turn. While the ultimate goal of the analysis of proteins and enzymes was to individualize blood, that's pretty much established with DNA technology. Within a year of the discovery, DNA typing was being put to the test in criminal cases. It not only cleared one man who had confessed to a crime, but also led to the conviction of the actual killer in the same crime. DNA can narrow down suspects in a hurry, but it's not foolproof. It can be challenged in court on the basis of sloppy evidence collection and the corruption of samples during testing. That was the tactic that O. J. Simpson's defense team used to win for him an acquittal in his double murder trial. Just how did they manage to accomplish this? To trace their strategy, let's look at the case. On the night of July 12, 1994, Nicole Brown Simpson and Ronald Goldman were slaughtered outside her Brentwood, California home. Nicole was the former wife of football celebrity O. J. Simpson, and he was called in from out of town for questioning. Going to his home on the night of the murder, detectives had noted a bloodstain on the door of his white Ford Bronco and a trail of blood leading up to the house. That was suspicious enough to start asking questions. When Simpson returned to Los Angeles, investigators noticed a cut on a finger of his left hand. He told several conflicting stories about how he had gotten it, which boxed him in later when blood at the crime scene indicated that the killer had been cut on his left hand and had trailed blood outside the gates. That hardly seemed coincidental. Then when several droplets of blood at the scene failed to show a match with either of the victim's blood types, Simpson's blood was drawn for testing (after the droplets had already been collected). Comparison between his DNA and that of the blood at the scene showed strong similarities. The tests indicated that the drops had three factors in common with Simpson's blood and only one person in 57 billion could produce an equivalent match. In addition, the blood was found near footprints made by a rare and expensive type of shoe-shoes that O. J. wore and that proved to be his size. Next to the bodies was a bloodstained black leather glove that bore traces of fiber from Goldman's jeans. The glove's mate, stained with blood that matched Simpson's, was found on his property. There were also traces of the blood of both victims lifted from inside Simpson's car and house, along with blood that contained his DNA. In fact, his blood and Goldman's were found together on the car's console. Forensic serologists at the California Department of Justice, along with a private contractor, did the DNA testing. Then other evidence emerged, such as the testimony of the limousine driver who came to pick Simpson up for the ride to the airport: On the night of the murder, while he waited for Simpson, he had seen a black man cross the driveway and go into the house. Then Simpson claimed that the driver had been unable to get him on the intercom because he had "overslept." So then who was the black man who had entered the house? When arraigned, Simpson pleaded Not Guilty and hired a defense team of celebrity lawyers. Barry Scheck and Peter Neufeld from New York were the DNA experts, renowned for their work on the Innocence Project, which used DNA analysis to defend the falsely accused. Scheck felt confident that they could produce challenges before the jury that would both educate and persuade them.
The reliability of this evidence came to be called the "DNA Wars," and three different crime labs performed the analysis. All three determined that the DNA in the drops of blood at the scene matched Simpson's. It was a 1 in 170 million match, using one type of analysis known as RFLP, and 1 in 240 million match using the PCR test. Nevertheless, criminologist Dr. Henry Lee testified that there appeared to be something wrong with the way the blood was packaged, leading the defense to propose that the multiple samples had been switched. They also claimed that the blood had been severely degraded by being stored in a lab truck, but the prosecution's DNA expert, Harlan Levy, said that the degradation would not have been sufficient to prevent accurate DNA analysis. He also pointed out that control samples were used that would have shown any such contamination, but Scheck suggested that the control samples had been mishandled by the lab-all five of them---and the jury bought it. The evidence was damning, but the defense team managed to refocus the jury's attention on the corruption in the Los Angeles Police Department. They then disputed the good reputation of the forensics labs, insisting that the evidence had been carelessly handled. Deliberating less than four hours, the jury freed Simpson with a Not Guilty verdict. They simply failed to understand how damning the DNA evidence really was and how ill fitting was the defense's logic about certain aspects of the blood at the crime scene. Nevertheless, it can certainly be the case that what appears to be overwhelming blood analysis evidence still fails to tell the whole story. We can see that in the next case, a family tragedy that happened in Australia.
near a dingo cave not far from the campsite. It was torn and bloodstained, but in good enough condition to be identified as the one Azaria wore the last time she was seen. It was sufficient for reasonable doubt and Lindy was released. The following year, the couple was officially pardoned. Not long afterward, their convictions were quashed. No matter how sophisticated the tests, interpretation is often subject to the narrative that the investigators build, especially if the evidence is ambiguous. It can only be hoped that future technology will eliminate the gray areas and provide more conclusive proof. http://www.crimelibrary.com/criminal_mind/forensics/serology/
The "Fatal Vision" Murders
February 17, 1970. It was one of the worst crime scenes that the Fort Bragg military officers had ever seen. Army doctor Captain Jeffrey MacDonald lay still but conscious on the floor of his master bedroom, while his murdered family was sprawled all over the house. He weakly asked how his kids were and said that he'd heard them crying. Colette, MacDonald's twenty-six-year-old pregnant wife, had been stabbed numerous times in the chest, and she lay bleeding underneath a torn blue pajama top that apparently had been worn by him. Above them both, written in blood on the headboard of the bed, was the word Pig, which was reminiscent of the vicious Manson murders in California only the year before. Colette's head showed evidence of severe blows with a blunt instrument, and both of her arms were broken. Down the hall in one bedroom was two-year-old Kristen. She had been stabbed thirty-three times in the chest and back, and her sister, five-year-old Kimberly, had been repeatedly stabbed and hit. Both were dead, and next to Kristen was a pool of blood near which a bloody footprint was visible. MacDonald's wounds were relatively minor (though he later claimed he'd been stabbed twenty-three times) and as police searched the house he told them what he could remember of the blitz attack. According to him, he'd been sleeping on the living room couch when Colette's cries woke him. Three men and a woman were standing in the living room, dressed like hippies and chanting, "Acid is groovy.kill the pigs." MacDonald said that he then tried to fight them, but they slashed him with an ice pick. In the process, he'd torn his pajama top and had then wrapped it around his hand to buffer the blows. Eventually the intruders knocked him unconscious with a baseball bat. When he came to, he found his wife and daughters bleeding from wounds and unresponsive to his attempts to revive them. He then made the emergency call that brought the MPs to his door. Detectives William Ivory and Franz Grebner made a thorough investigation of the crime scene and determined that MacDonald's story just didn't add up. The relatively minor disorder in the living room failed to support the description of a struggle between MacDonald and four other people. Even more suspicious to them was the fact that one of the magazines on the table had extensive coverage of the Manson murders, which bore obvious parallels to this incident. The whole thing was beginning to look staged. To the detectives' minds, it raised questions about why this gang of hippies on acid who'd stabbed MacDonald's family in such frenzy had allowed him to survive relatively unscathed, with some slight stab wounds and a few bruises. It was also troubling that MacDonald, who had terrible eyesight without his glasses, had been able to give such detailed descriptions of the perpetrators in his home. And why had he dialed the phone in the dark? When the MPs arrived, the house was dark. Then more evidence began to put MacDonald into a more suspicious light. On the bed where Colette had been attacked was the torn finger from a latex glove such as surgeons wears, and a knife that MacDonald claimed to have pulled out of his wife was clean of fingerprints. It also proved not to be the knife that had stabbed her. Also free of prints were both of the phones that MacDonald said he'd used to call for help. Even more troubling was the fact that several blue threads from the pajama top were found beneath Colette, although MacDonald had claimed to have simply laid the garment on top of her. Quite a few fibers were discovered below the headboard of the bed where "PIG" had been written by a right-handed person wearing something that resembled a glove. More fibers were found on a bloodstained piece of wood found in the back yard. Out there, they also found an ice pick and another
pick was being used to make one stab wound after another. The experiment also failed to account for the punctures in Colette's own pajama top, which was between her wounded chest and the jacket that her husband had laid on her. Even so, another prominent blood pattern analyst, Judith Bunker, had declined to serve on the defense, because she felt that her conclusions would not support their position. To understand how bloodstains at a crime scene can be open to debate, it's instructive to see where forensic blood analysis got its start. http://www.crimelibrary.com/criminal_mind/forensics/serology/
Putting it All Together
Several different blood analysis techniques came together in the Caren Campano case to provide enough evidence for an arrest. She was missing and there seemed to be nothing amiss in the home at first. Her husband, Chris, admitted that they'd had a fight just before she had disappeared on July 1, 1992, from their Oklahoma City home. He offered to let investigators look around, which was his first mistake. A huge brownish patch on the bedroom carpet alerted them to the possibility that it was blood. They used several techniques to find out more:
- A hema stick (microcrystal test) This stick is coated with a blood-sensitive chemical which, when touched to a substance and then sprayed with distilled water, indicates the presence of blood. Later in the lab, they determined that it was human blood.
- Luminol Although the house appeared to be spotless, when this highly sensitive chemical was sprayed around the room in the dark, it illuminated so many areas that it was clear that a virtual bloodbath had taken place. When blood flies through the air, the pattern in which it lands can determine its track, as well as the location and position of the weapon that inflicted the blow. It can also provide an estimate of how many blows were struck. Investigators found spatters on the walls, doors, and even across the ceiling. There was also a blood trail through the house and down the back outside steps. Piecing together from the splatter patterns what might have occurred, they felt certain that the victim had received numerous blows to the head with a blunt object, which collectively would have been fatal.
- Blood Volume Test through stain recreation On the same rug, they poured the amount of blood that would have been needed to make a stain the same size as the one they found, and then estimated that a person the size of Caren Campano would have lost at least 40% of her blood. She could not have survived that.
- DNA analysis - Reverse paternity test Although Caren's father was deceased and they had no samples of her DNA, they took blood samples from as many members of her family as they could find, hoping for a partial match with all of them. Finding it, the police had enough for an arrest on the suspicion of murder. Finally, a year after her disappearance, they located Caren's remains, which by this time were mostly skeletal. The dental records matched and the story told by the many fractures to the skull confirmed the theoretical scenario pieced together from the blood spatters in the Campano bedroom. Chris Campano was then convicted of the murder of his wife. The various tests used on blood and blood patterns can offer crucial evidence in the reconstruction of a crime scene and even the proof of murder without having the body. http://www.crimelibrary.com/criminal_mind/forensics/serology
The Poisoned Needle
How techniques for separating mixtures helped solve a deadly mystery One morning in the summer of 1961, hundreds of crazed birds attacked the seaside town of Capitola, California. The birds "cried like babies" as they dove into streetlamps, crashed through glass windows, and attacked people on the ground. Most of the birds were sooty shearwaters, a normally non- aggressive species that feeds on small fish and comes ashore only to breed. The incident fascinated Alfred Hitchcock, who frequently vacationed in nearby Santa Cruz. He included newspaper clippings about the Capitola attack in his studio proposal for The Birds, which appeared in cinemas two years later. In the winter of 1987, the agent that is now believed to be responsible for the Capitola incident struck on the opposite shore of the continent. This time, it struck higher on the food chain. Over a hundred people became extremely ill within hours after dining on cultured blue mussels in restaurants around Prince Edward Island in Canada. It quickly became apparent that this was no ordinary outbreak of food poisoning. Vomiting, cramps, diarrhea, and incapacitating headaches were followed by confusion, loss of memory, disorientation, and (in severe cases) seizures and coma. A few exhibited emotional volatility, with uncontrolled crying or aggressiveness. Three elderly victims died. [Perl]. A tragic symptom of poisoning was the destruction of short term memory in about one quarter of the survivors. They could remember nothing that happened after the poisoning. Some were unable to recognize their surroundings or relatives. They could learn no new facts or skills. The most severely affected lost memories several years old. For twelve of the victims, the loss of short term memory was permanent. The mysterious syndrome was called "amnesic shellfish poisoning". This sort of neurological damage due to food poisoning had never been encountered before. To prevent further injury and loss of life it was imperative that the toxic agent be isolated and identified as quickly as possible. A team of marine biologists and chemists was assembled by Canada's Department of Fisheries and Oceans (DFO) to work on the problem. But quick resolution of the mystery was unlikely. An initial screening of the sample for known bacterial and viral pathogens revealed nothing. Tests for heavy metals, pesticides, and PCBs also were negative. The mussel samples were extremely complex, containing thousands of different chemical compounds. How can one component be isolated from a such a complex mixture, without knowing anything about its physical or chemical properties? How do you find a needle in a haystack, when you've never seen a needle before? Suppose a test could be devised for the presence of the needle in a haystack. The haystack could be divided in half, and the half that tested negative for the needle could be discarded. Repeating this divide-and-discard process over and over again should eventually result in a pile with only one thing left: the needle. That was the strategy the researchers used to isolate the toxin. A reliable but gruesome biological test was developed. Injection of a small amount of the sample into mice produced a very distinctive neurological reaction if the toxin was present: the mice involuntarily scratched their shoulders with their hind legs. [Teitelbaum] Standard physical methods for separating complex mixtures were applied to the poisoned mussel
samples. At the same time, uncontaminated mussels were subjected to the same separations, to allow the analysts to compare fractions. Any differences in spectra or chromatograms between the control and toxic samples might be valuable clues in the search for the toxic agent. Mice were exposed to each fraction of the separation. Fractions found to be toxic were retained for further analysis. The others were discarded. If chromatograms and spectra indicated that the toxic fraction was still a complex mixture, another separation technique was applied. Separation by solubility and volatility Most drugs and poisons are either fat soluble or water soluble, so a logical first step in the isolation was solvent extraction. To prevent potential decomposition of the compound by heat or harsh solvents, ground mussel samples were extracted at room temperature with aqueous methanol, a mild solvent. The extraction was inefficient but successful: mice had the same neurological reaction to the methanol extract that they had to the original mussel samples. The extract was concentrated by evaporation. The vapor was not toxic, but the residue after evaporation was. The poison apparently was nonvolatile, which could indicate a high molecular weight compound, or a compound that ionized in solution. A second extraction was performed by shaking the concentrated extract with a mixture of a nonpolar solvent (dichloromethane and water, which is polar. The two solvents don't mix; they settle into two easy separable layers. The dichloromethane fractions for the toxic mussels contained several colored substances absent in the control mussels. The visible light absorption spectrum revealed a pattern of absorptions that are characteristic of phytoplankton pigments. An initial examination of the toxic mussels revealed that they were engorged with green plankton, while the nontoxic mussels weren't. This was an important clue in the search for the origins of the toxin. But the pigments themselves were not poisonous. The dichloromethane fraction gave a negative result in the mouse bioassay. The aqueous layer contained the toxin, indicating that it was probably a polar, ionizable substance. This was a lucky break, because the researchers could discard the complex dichloromethane fraction and concentrate on the much simpler aqueous fraction. Separation by polarity Column chromatography was used to separate the aqueous layer into simpler components. The sample was passed through a narrow tube packed with beads of a resin called XAD-2, which grabs the nonpolar parts of passing molecules, but lets ions pass freely. XAD-2 chromatography is particularly effective for separating organic acids and bases. Flushing the resin with a strong base ionizes acids in the sample. The ionized acids will pass through the column before other organic compounds because the resin won't retain them in their polar ionized form. Flushing with a strong acid gives organic bases in the sample extra hydrogen ions (and a positive charge); any organic bases adsorbed onto the resin will be washed out of the column. Of the many fractions that passed out of the XAD-2 column, only one was toxic. For the final stage of the purification, the toxic fraction was separated with high performance liquid chromatography (HPLC). Again, a polar solution containing the sample was passed through a column packed with a nonpolar stationary phase. A single, highly purified fraction collected from the HPLC column accounted for all of the toxicity present in the original mussel sample. The toxin was isolated. Separation by charge, size, and molecular shape The researchers had to ensure that the final HPLC fraction was indeed the isolated toxic component. They separated the aqueous XAD-2 fraction again, using a completely different technique: high voltage paper electrophoresis.
Domoic acid's structure is obviously similar to glutamic acid. But its five-sided ring makes it less flexible than glutamate, which causes it to bind very tightly to glutamate receptors. As a result, the excitatory effect of domoate is 30 to 100 times more powerful than that of glutamate [Perl]. How did the domoic acid get into the shellfish (and the anchovies eaten by the birds at Capitola)? Remember that phytoplankton pigments were found in the aqueous layer after solvent extraction. This wasn't quite a smoking gun, but it was definitely a fingerprint of the killer. An extensive investigation traced the domic acid to an obscure species of needle-like diatom*, called Pseudo-nitzschia pungens. Pseudo-nitzschia has been found in oceans around the world, so further outbreaks are possible in many locations. Commercial shellfish and seafood is now monitored regularly for domoic acid, using HPLC to identify the toxin. The screening and testing procedures have so far been successful- not a single instance of domoic acid poisoning in humans has been reported since the 1987 outbreak. The original article and its references can be viewed at this address.
