March 3, 2016 by Locard's Lab

Forensic Failures: Three Men, Three Hairs, Three Wrongful Convictions

In the summer of 1978, 63-year-old taxi driver John McCormick was robbed and shot on his own doorstep in his Washington, D.C home. His wife, roused from sleep by the cries of her husband pleading for his life, ran to his aid to briefly glimpse the gunman, a man with a stocking mask shielding his face. McCormick died as a result of the attack, shot by a .32 calibre handgun. A police officer and his dog later found the stocking mask nearby, and from this a number of hairs were recovered.

Santae Tribble (Source: The Innocence Project)

Suspicion soon fell on 17-year-old Santae Tribble, implicated by an informant, Bobby Jean Phillips, who claimed Tribble had recently sold a .32 calibre handgun to her roommate. A weapon that, incidentally, was never successfully linked to the gun used to kill McCormick. Tribble was pulled in for questioning. Hairs recovered from the stocking used by the killer were compared to samples collected from the suspect and, according to an FBI analyst, “matched in all microscopic characteristics”. At trial, the prosecution went on to declare that there was perhaps a “one chance in ten million” that the hair belonged to someone else. Seemingly compelling “statistics” and apparently sufficient in helping the jury reach a verdict. Despite having testified that he was in Maryland at the time of the attack, an alibi supported by half a dozen witnesses, in January 1980 Santae Tribble was found guilty of murder and sentenced to 20 years to life in prison.

Meanwhile, as Tribble was adjusting to prison life, another man’s world was about to be turned upside down thanks to a single hair. In February 1981, a 27-year-old woman was bound, raped and robbed in her apartment, briefly glimpsing her attacker in the dim light. The distraught victim helped police construct a composite sketch of her attacker; a young, cleanly shaven African American man. Unfortunately for 18-year-old Kirk Odom in the following weeks, a passing police officer decided that Odom resembled the composite sketch, passing on his suspicions to the detective leading the case. As a result of this Odom was presented to the victim as part of a somewhat dubiously organised line-up, with Odom standing on a box in order to match the height of the other men in the line-up, who were actually police officers. The victim identified Odom as her attacker.

Kirk Odom (Source: The Innocence Project)

During the trial, FBI Agent Myron Scholberg testified that the “Negroid hair” found on the victim’s nightgown was microscopically similar to a hair sample taken from Odom, “meaning the samples were indistinguishable”. He declared this to be “a very rare phenomenon”, and in the thousands of occurrences in which he had compared hair samples, on only eight or ten occasions had he failed to distinguish the hairs of two different people. Understandably, this implied a very substantial likelihood that the hair did in fact belong to Odom, and after only a few hours deliberating he was found guilty and sentenced to 20 to 66 years in prison.

In June that same year, a worryingly similar scenario ensued after 21-year-old student Catherine Schilling was found raped and murdered in Rock Creek Park, Washington. She was discovered naked and shot five times in the head. A somewhat questionable police informant, Gerald Mack Smith, relayed to police that he had been drinking in the park with a man who had admitted to killing the woman after attempting to rob her. That man was allegedly Donald Eugene Gates. It is worth noting that, not only was Smith paid by police for his information, but at the time he had two prior felony convictions and had recently been indicted for a third felony, which was conveniently dismissed after he aided the police in incriminating Gates. This information was not relayed to the defence team.

Donald Gates (Source: The Washington Post)

So Donald Gates, aged 30 at the time, was arrested and charged with murder, not only based on the testimony of Gerald Smith, but also largely on the comparison of hair samples. FBI forensic analyst Michael Malone testified in this case, establishing that hairs recovered from the scene were “microscopically indistinguishable” from a hair sample taken from Gates. The expert witness claimed that in his many years of hair comparison work, there were perhaps two in ten thousand cases where hairs from two people could not be distinguished. Once again, seemingly convincing statistics to a lay jury. In September 1982, Gates was found guilty and sentenced to 20 years to life in prison.

Forensic Hair analysis

What do these three cases have in common? All men were wrongfully convicted for crimes they did not commit. And all convictions were largely based on flawed expert witness testimony relating to hair analysis.

The potential evidential value of human hair stems from its prevalence at crime scenes and the ease with which it can be imperceptibly transferred. It is fairly resilient and can persist at a crime scene for many years after the incident took place, all-in-all making hair a potentially vital piece of evidence well worthy of examination.

What does this examination involve? Forensic hair analysis is a type of ‘comparison analysis’ – that is an examination that is typically based on individual or class characteristics rather than incorporating numerical analyses. It generally involves the study of microscopic characteristics relating to whether the hair is human or animal, the colour, length, diameter, likely racial group, area of bodily origin, phase of growth, and so on.

Microscope image of hair sample

The examination may include an even closer scrutiny of patterns and intricacies along the shaft of the hair. The human hair can be described as being composed of three distinct regions: the medulla, the cortex and the cuticle. The medulla refers to the inner core of the shaft, the cortex as the surrounding material, and the cuticle the outermost protective layer. The cuticle is composed of a scale-like complexion, which can be particularly beneficial in distinguishing between animal hairs and human hairs. Cuticle characteristics will be noted in the comparison of hair samples, particularly the thickness of the cuticle, the colour, and the general shape of the “scales”. The cortex is the portion of the hair containing pigment granules which give hair its colour, obviously vital in the comparison of different samples. These pigment granules vary between racial groups, thus are pivotal in establishing whether a hair is likely Caucasian or Negroid in origin, for instance. The medulla in the centre of the hair shaft will also be scrutinised to determine whether the core is continuous, interrupted, fragmentary or absent.

This is a limited list of the features focussed on during forensic hair analysis. In reality there is a myriad of other features, both natural such as those above and artificial such as dyeing and damage, that can be used in studying the similarities and differences between hair samples. So it would seem there is an abundance of information with which to reach a conclusion. However the problem lies in that these are all class characteristics whose description is based on the individual analyst’s subjective observations.

Obviously the ideal situation would involve some form of statistical analysis to determine the reliability of comparisons, but the vast number of variable factors in hair comparison makes statistical analysis tremendously complex if not impossible. This in itself does not render such analyses worthless in criminal proceedings, provided accurate testimony is given and caveats made clear. In the aforementioned cases, and potentially others, expert witness testimony strongly implied that exact matches between hair samples had been made, and in some instances fictitious statistics were even expressed to the jury. When such evidence is presented by a seemingly distinguished scientist who may be an expert in their field, naturally members of a lay jury with little or no knowledge of the topic are unlikely to challenge this evidence. The FBI’s own guidelines on forensic hair analysis conclude that “the science of microscopic hair examination can never result in an identification” but can “provide a strong basis for an association”, but unfortunately this ethos was not always carried into the courtroom.

Collectively, Tribble, Odom and Gates served nearly 80 years in prison. All three men were eventually released and exonerated by DNA testing and the actual perpetrators identified. However by the time this was achieved, perpetrators had passed away or were able to evade conviction due to expiration of the statute of limitations. The wrongfully convicted men were awarded millions of dollars in compensation, but hardly a prize worthy of losing so many years.

As a result of these incidents, and numerous others, ongoing investigations are aiming to identify further miscarriages of justice in the United States, initially largely powered by the Innocence Project, a non-profit organisation which aims to exonerate wrongly convicted people through DNA testing. Furthermore, efforts are underway to focus on how forensic science standards can be strengthened to avoid future errors, particularly in relation to forensic ‘comparison analyses’.

References

Federal Bureau of Investigation. Forensic hair comparison: background information for interpretation. [online] Available: https://www.fbi.gov/about-us/lab/forensic-science-communications/fsc/april2009/review/2009_04_review02.htm

Innocence Project. Donald Eugene Gates. [online] Available: http://www.innocenceproject.org/cases-false-imprisonment/donald-eugene-gates

National Registry of Exonerations. Kirk Odom. [online] Available: https://www.law.umich.edu/special/exoneration/pages/casedetail.aspx?caseid=3943

Taupin, J. M. Forensic hair morphology comparison – a dying art or junk science? Sci & Justice. 44 (2004), pp. 95-100.

The Washington Post. Santae Tribble cleared in 1978 murder based on DNA hair test. [online] Available: https://www.washingtonpost.com/local/crime/dc-judge-exonerates-santae-tribble-of-1978-murder-based-on-dna-hair-test/2012/12/14/da71ce00-d02c-11e1-b630-190a983a2e0d_story.html

June 2, 2015 by Locard's Lab

Colin Pitchfork & The Début of DNA Fingerprinting

DNA fingerprinting, the process of producing a unique ‘fingerprint’ from a DNA sample, is something of a staple in forensic science. The ability to link a suspect to a crime scene or identify a set of remains has revolutionised legal investigations, being utilised in countless legal cases across the world since its discovery in 1984.

But once upon a time this renowned technique was just emerging, with its creator, geneticist Sir Alec Jeffreys of the University of Leicester, still unaware of just how beneficial his new technique would be to the criminal justice system. But how did this somewhat stumbled upon discovery end up becoming one of the most reliable forensic techniques available?

The story begins in late November 1983. 15-year-old Lynda Mann set off from her home in a small Leicestershire village to visit a friend, but unusually did not return. The following morning her raped and strangled body was found on a quiet footpath. Little evidence could be found other than a semen sample retrieved from her remains, though even this proved to be ineffective in leading investigators in the right direction.

But this would not be the last the world would hear of Lynda Mann. Just a few years after Lynda’s murder, another young girl went missing in July 1986. 15-year-old Dawn Ashworth had been walking home when she disappeared, her family’s worst fears soon confirmed when her brutally raped and strangled body was found two days later in the woods. Once again, a semen sample was found on the victim. The similarities between the two murders were not overlooked and, with a fresh influx of interest and evidence, the investigation could progress, with police believing the same man could be responsible for both crimes. Suspicion soon fell on Richard Burkland, a 17-year-old local who appeared to have suspicious knowledge of the latest incident. Under questioning he admitted to murdering one of the victims. Job done, the police might have thought.

Source: http://www.sciencemuseum.org.uk

Meanwhile at the University of Leicester Sir Alec Jeffreys and his team were working on a novel DNA fingerprinting technique. The technique had already been utilised in an immigration case involving a boy from Ghana, successfully proving that he was in fact the son of a family living in the UK. Recognising the potential power of this procedure and keen to apply it to a criminal case, investigators pulled Jeffreys’ and his new technique into the case.

Contrary to the belief of police, DNA profiling actually proved that Richard Burkland’s DNA did not match the semen found at the two crime scenes, pushing the investigation back to square one. Although this in itself was a ground-breaking scenario, the first ever exoneration of an innocent man using DNA fingerprinting, the murderer was still at large and the police had no more leads to follow.

With no other options, on 1^st January 1987 Leicestershire Constabulary announced that they would be joining forces with the Forensic Science Service to conduct a huge DNA profiling project, collecting DNA samples from over 4000 local men in order to rule them out as suspects. However six months down the line a match had not been found. Were their efforts all for nothing?

Fortunately, a lucky break came from a particularly interesting conversation overheard in a local pub. Ian Kelly, an employee at a nearby bakery, was caught bragging about being paid £200 to submit a DNA sample on behalf of a work colleague. Living too far away from the area to have been required to give a sample himself, Kelly had apparently agreed to this request without many questions. Unsettled by the conversation, another employee soon raised the alarm, and Kelly was detained and questioned.

Source: http://www.express.co.uk

Kelly was covering for Colin Pitchfork, a local baker. Pitchfork had convinced Kelly that he would be framed for murder if his own blood sample was submitted, a story which was evidently enough to persuade Kelly to oblige.

On 19^th September 1987, Pitchfork was arrested. After the new DNA profiling technique matched his DNA fingerprint to the crime scene samples, he admitted to raping and killing the two girls. Experts calculated the probability of this match occurring by chance to be 5.8 x 10^-8. Pitchfork was sentenced to life imprisonment on 23^rd January 1988.

Moral of this story – if you think you’ve gotten away with murder, you had better hope your mates don’t chat about it at the pub.

References

Bodmer, W. F. et al. 1994. The Book of Man: The Human Genome and Our Quest to Discover our Genetic Heritage. Oxford: Oxford University Press.

R v Pitchfork 2009

Featured Image: DNA Testing. [online] Available: http://upoa.biz/dna-testing

April 10, 2015 by Locard's Lab

Forensic Case Files: Bruce Ivins and the Anthrax Attacks

In September 2001, when the US was still reeling from the notorious 9/11 terrorist attacks, two US Senators and various media organisations were sent letters containing spores from the bacterium Bacillus anthracis, the cause of the disease Anthrax. The malicious mail resulted in the deaths of five people, the infection of 17 others and an investigation between the FBI and the US Postal Inspection Service that spanned almost 7 years.

Bacillus anthracis is a rod-like bacterium which can, upon entering the body, bring about the acute disease known as Anthrax. The endospores (spores) of the bacterium can lay dormant for years, but become activated and multiply after coming into contact with a host. Once contracted, the symptoms of the disease are dependent on the route by which the bacteria entered the body. However left untreated, the disease can ultimately kill the host.

The mailed anthrax spores were accompanied by misleading letters suggesting the attack was motivated by religion, though the prospect of terrorist groups, that were already at the forefront of the country’s mind, were soon discounted. It was soon concluded that a likely source of the anthrax, which was of the Ames strain, had been maintained by the US Army Medical Research Institute of Infectious Diseases (USAMRIID). Suspicion fell on Dr Bruce Ivins, who had been a researcher at the facility. Whilst in this position, Ivins had created and maintained this particular spore-batch, suspected to have been the batch used in the anthrax attack. With suspicions supported by an array of incriminating circumstantial evidence, investigators called upon a team of scientific experts to establish whether there was a link between Ivins’ own anthrax and the mailed anthrax.

Traditional forensic techniques were used in the examination of the spore powder and the letters and envelopes, including fingerprinting, and hair and fibre analysis, though this did not lead to any major breakthrough. A suite of analytical techniques was employed to ascertain various facts regarding the anthrax. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to identify the size, shape and quality of the anthrax spores, as well as provide a profile of the chemical elements within the spores. SEM and TEM are microscopy techniques which employ a focused beam of electrons which interacts with the atoms of the sample, allowing it to be visualised. They can be coupled with energy-dispersive X-ray (EDX) spectroscopy to provide elemental analysis. The physical and chemical characteristics of the spores allowed investigators to presume that the anthrax was not weapons-grade, but it was of a concentration and quality similar to that used in bio-defence research.

Inductively coupled plasma optical emission spectroscopy (ICP-OES), a technique based on the emission of photons from substances, was used to provide further details of the elemental composition of the spore powder. Furthermore, gas chromatography mass spectrometry (GC-MS) was employed to characterise the spores. Experts at the Center for Accelerator Mass Spectrometry (CAMS) were called upon to analyse the anthrax spores and establish their relative age. Accelerator mass spectrometry turns a sample, which has been converted into solid graphite by the analyst beforehand, into ions and accelerates these ions to high kinetic energies before conducting mass analysis to detect C¹⁴ (and potentially other isotopes depending on the work) to estimate the age of a sample. The analyses carried out on the samples in this instance determined that the mailed anthrax has been produced within 12 months of the attack, narrowing down the possible sources and suspects.

But perhaps the biggest breakthrough in the case came from a newly developed DNA fingerprinting technique which allowed investigators to conclude that the blend of anthrax spores created by Ivins in the lab was identical to that used in the attack, though how unique this “genetic signature” was has been somewhat debated. The US Justice Department later concluded that Ivins was solely responsible for the preparation and mailing of the deadly spores, claiming that he believed the scare would resurrect his anthrax vaccine program. Ivins later died from an overdose, deemed to be a suicide.

The case of Dr Ivins and the anthrax letters is a great example of how different analytical techniques can be drawn together to work in perfect harmony, utilising their individual powers to find out everything there is to know about a sample. In this case the array of techniques used allowed investigators to discover what the spores looked like and what they were composed of, their concentration and quality, and even how old they were. Armed with this information, investigators could home in on the source of the anthrax spores and the man behind the attack.

References

Centre for Infectious Disease Research and Policy. FBI says it easily replicated anthrax used in attacks.

US Department of Justice (2010). Amerithrax Investigative Summary. Darby, PA: DIANE Publishing.

Washington Post. FBI investigation of 2001 anthrax attacks concluded; U.S. releases details. [online] Available: http://www.washingtonpost.com/wp-dyn/content/article/2010/02/19/AR2010021902369.html