Chemistry Against Crime
Walter F. Rowe
Professor of Forensic Sciences
George Washington University
About the Lecture
The popular TV program CSI has sparked interest in forensic chemistry; this lecture tells what it’s really like. Forensic chemists may find themselves analyzing a wide variety of samples: solid dosage forms of drugs, trace evidence (including glass, soil, hairs, fibers, paint and plastics), ignitable liquid residues, explosive residues and gunshot residues. Because they deal with such a wide array of possible samples, forensic chemists must be familiar with many different analytical tools such as chromatography and spectroscopy. They must also know how to use polarized light microscopes and scanning electron microscopes. However, the most important tool of the forensic chemist is careful scientific reasoning. The chain of reasoning will be demonstrated by a series of cases in which the author was able to uncover the truth about what had happened. These cases include a simple slip-and-fall accident, contamination of a shipment of industrial solvent and a death caused by a model airplane.
About the Speaker
WALTER F. ROWE is Professor of Forensic Sciences at George Washington University, where he has been a member of the faculty of the Department of Forensic Sciences for over thirty years. He served two years in the US Army crime laboratory system as a forensic drug chemist and forensic serologist. He has been a consultant forensic scientist to law enforcement agencies, prosecutor’s offices and defense attorneys. He has also worked closely with Barry Scheck and Peter Neufeld of the Innocence Project. He has contributed chapters to monographs and textbooks in forensic science, including one of the two main textbooks used for undergraduate instruction in the field of forensic science. He is a Fellow of the American Academy of Forensic Sciences and a former member of the editorial board of the Journal of Forensic Sciences. He is also a member of ASTM Committee E30, which sets standards (including educational standards) for a variety of forensic science disciplines. He is a member of the Council of Forensic Educators and is a past president of that organization. He has a B.S. degree in chemistry from Emory University and M.S. and Ph.D. degrees in chemistry from Harvard University.
President Ruth McDiarmid called the 2,220th meeting to order at 8:16 pm March 30, 2007 in the Powell Auditorium of the Cosmos Club. The recording secretary read the minutes of the 2,219th meeting and they were approved.
Ms. McDiarmid made announcements. She spoke of the traditional purpose of the Society, communication. She encouraged people to bring friends, family and colleagues to meetings. She reminded us that contributions are tax exempt and invited us too consider sponsoring meetings. She made the parking announcement. She told us how to find membership applications, and she encouraged us to volunteer to participate in a study led by the previous speaker, Monica Skarulis, at NIH.
Ms. McDiarmid then introduced the speaker of the evening, Mr. Walter F. Rowe, professor of forensic science at George Washington University. Mr. Rowe spoke on Chemistry Against Crime.
“You’ve seen the CSI effect,” Mr. Rowe began. He called CSI the most popular TV program in the world, counting its spinoffs. It also has imitators in other media, including comic books. He, himself, was recently tempted to order a crime-solving kit.
About 40% of that TV forensic science does not exist. Whether it ever will is doubtful. Unfortunately, juries actually expect CSI-like evidence.
CSI is the modern equivalent of Sherlock Holmes. Mr. Rowe gave examples of thrilling crime-solving reported in popular media going back to the 1930’s.
We still do some of that stuff, he said. One example, reported long ago under a colorful headline, was restoring serial numbers ground off of a pistol. That is now considered routine. One old headline said, “Weird, Unseen Rays Trap Master Crooks.” Those “weird” rays were ultraviolet light. Today they still use them, as well as other parts of the light spectrum, to reveal things not visible under normal spectra.
Accustomed to defending his credibility, he told us his background. He started as a U.S. Army criminal investigator. His credibility did suffer a bit when he showed us the logo of his army specialty featuring Mickey Mouse in the middle. He moved on to forensic chemistry lab work. Today, in addition to being a professor at GW, he is a fellow of the criminalistics section of the American Association of Forensic Sciences. He has worked on some notable cases such as the Jeffrey McDonald case, the Dale Earnhart death and the exhumation of Jesse James.
He defined forensic science as the application of scientific principles to resolution of legal issues, civil, criminal, and administrative. The work is chemical analysis, firearm and tool mark work, document examination, fingerprint identification, and photography and image analysis. Most practitioners work in police crime labs. There are subspecialties, notably forensic pathology, odontology, anthropology, toxicology, psychiatry, and psychology. They do a lot of work in drug chemistry, trace evidence analysis, hairs and fibers, glass and soil, paint and plastics, ignitable liquids, explosive residues, and forensic biology. They do testimony, documentation, and demonstrative diagrams and charts. Often, the purpose is to prove the elements of a crime, identify a perpetrator or to confirm or refute the statements of complainants.
He mentioned one of the old adages of forensics called the Locard exchange principle -- when two surfaces come in contact, an exchange of trace evidence takes place. The way Henri Locard expressed it was, “Every touch leaves a trace.”
He showed how a shoe impression can be treated with various substances called amido black, Hungarian red, Crowle’s stain, and coomassie blue. Some substances allow the impression to actually be lifted, with adhesives, and taken away. Crystal violet, the main chemical of the old mimeograph print process, is often used to take shoe impressions.
Blood releases oxygen atoms. This property is used to differentiate blood stains from similar looking stains and also to localize blood among other stains. They spray it with a luminol, shine a light on it, and it glows brightly.
He discussed Dale Earnhart’s death. Nascar champion Earnhart hit the wall in his racer at a speed that need not have caused death. His restraint harness broke and some people suspected foul play.
Mr. Rowe demonstrated the blood was human and that the DNA matched Earnhart’s. The safety strap, designed for 5000 pounds, failed at 2000 because it was installed wrong. The stress focused on the edge instead of distributed across the strap. Also, the matting at the end of the belt indicated the belt tore before Earnhart was injured and began bleeding.
Mass spectrometry is very useful in identifying substances. Each substance has molecular ion peaks at precise points, and the pattern is definitive. This is important because there are significant differences in penalties for different, related substances, as well as the fact that the whole case can turn on a proper identification.
The Jeffrey McDonald case illustrated this. McDonald claimed drug-crazed hippies broke into his home, killed his wife and children, tied him up and wounded him slightly. His defense argued that orlon fibers identified in the analysis must have come from wigs worn by people posing as hippies. This reasoning was undercut by the fact that McDonald’s wife also had orlon fiber wigs.
He described a civil case wherein a laboratory tested a shipment of linear alkyl benzene (LAB) and found it was contaminated with “amphetamines and other unidentified substances.” After a year without resolution, the consignee of the shipment sold the lot at a loss and filed an insurance claim. The insurance company engaged Mr. Rowe, who found that the first analysis was simply erroneous. The only contaminant was water. Since a little water is normal in this situation, the shipping company was not at fault.
Then he discussed the exhumation of the body alleged to be, and alleged by others not to be, Jesse Woodson James. He showed a picture of the famous James in his coffin, looking dapper and well preserved. The picture was taken before he was buried. The picture showed no hematoma on the front of the head although Mr. James had been shot in the back of the head.
The reasons for doubt about Mr. James’s death seemed somewhat insubstantial. Archeological evidence from the James farm included “suspected human hairs,” suggesting a different person had been buried there. A man thought to be James was seen in Garland, Texas after James’s “death.”
Mr. Rowe’s analysis of the remains in Jesse James’ grave found the hairs there were human, they were from a Caucasian, and the hairs had been dyed with boot black, as Jessee had done while in hiding. Most telling, mitochondrial DNA sequencing from the hair was accomplished and it matched sequences from James family members. A body dug up in Garland did not match Mr. James’ characteristics.
To bring us back to the mundane world, he described a classic slip and fall accident. A woman had fallen, she claimed, on ice. The landlord, who was sued, picked up her shoe from the site. It had a broken sole, which she said had broken when she fell. The landlord’s lawyer wanted it tested to see what force it would take to break it. Mr. Rowe dissuaded him from that course, but offered to analyze the scratch patterns on the sole. Some of the scratches continued across the break and some did not, and some of those which did had been worn away near the break by the additional stress there. Also, there was moisture in the shoe which had apparently entered through the broken sole. With this evidence of a cause of the fall unrelated to ice, the landlord’s lawyer was able to reach a reasonable settlement.
Mr. Rowe also described his analysis of a model airplane that had hit a man and killed him. The plane owner reported having reglued the tail. Mr. Rowe found it had been reglued three times with two different kinds of glue. This established some culpability of the owner.
Mr. Rowe described his work to identify different kinds of permanent markers from the marks they leave. It seems that the different frequency distributions of light of different makes of markers distinguish them pretty well. He used principal component reduction analysis to establish this.
Mr. Rowe offered to take questions.
Someone asked about dermal nitrate tests (gunpowder residue tests) on Lee Harvey Oswald. Mr. Rowe thought they had been done, but the methodology was not well understood at the time, and they learned nothing by doing the tests.
Along that line, someone pointed out that there had been problems reported in FBI labs in the 1970’s. Mr. Rowe agreed emphatically and added that the problems did not end in the ‘70’s. He gave several examples of horrible performance of crime labs. In West Virginia, a Court of Criminal Appeals gave habeus corpus writs to 130 persons who were convicted on the testimony of one discredited forensic scientist.
After the discussion, Ms. McDiarmid presented a plaque to Mr. Rowe commemorating the occasion. She invited everyone to stay for the social hour. At 9:47 pm, she adjourned the 2,220th meeting.
Temperature: 13° C
Weather: Clear, bright, moon nearly full.
Ronald O. Hietala