forensic evidence

Problems with Forensic Expert Testimony in Arson Cases

by Becky Huting, UMN Law Student, MJLST Staff

In MJLST Volume 14, Issue 2, Rachel Diasco-Villa explored the evidentiary standard for arson investigation. Ms. Diasco-Villa, a lecturer at the School of Criminology and Criminal Justice at Griffith University, examined the history of arson-investigation knowledge, and how the manner in which it is conveyed in court can mislead, possibly leading to faulty conclusions and wrongful convictions. The article discussed the case of Todd Willingham, who was convicted and sentenced to death for setting fire to his home and killing his three children. Willingham had filed numerous unsuccessful appeals and petitions for clemency, and several years after his execution, a commission’s investigation concluded that there were several alternative explanations as to the cause of the fire, and that neither the investigation nor the evidence testimony were compliant with existing standards.

During the trial, the prosecutor’s fire expert, a Deputy Fire Marshall from the State Fire Marshall’s Office, testified as to why he believed the fire was set by arson. Little science was used in his explanation:

Heat rises. In the winter time when you are going to the bathroom and you don’t have any carpet on the rug. . .the floor is colder than the ceiling. It always is. . . So when I found that floor is hotter than the ceiling, that’s backwards, upside down. . .The only reason that the floor is hotter is because there was an accelerant. That’s the difference. Man made it hotter or woman or whatever.

The expert went on to explain that fire investigations and fire dynamics are logical and common sense, such that jurors themselves could evaluate with their sense and experiences to arrive at the same conclusions. All samples taken from “suspicious” areas of the house tested negative for any traces of an accelerant. The expert explained the chemical results: “And so there won’t be any — anything left; it will burn up.”

Fire and arson investigation has traditionally been experiential knowledge, passed down from mentors to their apprentices without experimental or scientific testing to validate their claims. Fire investigators do not necessarily have scientific training, nor is it necessary for them to hold a higher educational degree beyond a high school diploma. The National Academy of Science released a report in 2009 stating that the forensic sciences needed standardized reporting of their findings and testimony, and fire and arson investigation was no exception. The International Association of Arson Investigators has pushed back on such guidance, having filed an amicus brief arguing that arson investigation is experience-based and not novel or scientific, so it should not be subjected to higher evidentiary standards. This argument failed to convince the court, which ruled that fire investigation expertise should be subject to scrutiny under the Daubert standards that call for exacting measures of reliability.

Ms. Diasco-Villa’s note also considers the risk of contextual bias and overreach, should these experts’ testimony be admitted. In the Willingham case, the expert was given wide latitude as to his opinion on the defendant’s guilt or innocence. He was allowed to testify as to his belief that the suspect’s intent “was to kill the little girls” and identify the defendant by name as the individual who started the fire. Under Federal Rules of Evidence section 702, expert witnesses are given a certain degree of latitude in stating their opinions, but the author was concerned with the risk of jurors giving extra weight to this arguably overreaching testimony by expert witnesses.

She concluded by presenting statistics concerning the vast number of fires in the United States each year (1.6 million), and the significant quantity that are classified as having been intentionally set (43,000). There is a very real potential that thousands of arrests and convictions each year may have relied on overreaching testimony or evidence collected and interpreted using a defunct methodology. This state of affairs in arson investigations warrants continued improvements in forensic science techniques and evidentiary standards.


Chimeras in DNA Forensic Testing: What to do?

by Ryan J. Connell, UMN Law Student, MJLST Staff

Thumbnail-Ryan-Connell.jpgThe answer as suggested in an essay titled Chimeric Criminals by David H. Kaye in the current issue of the Minnesota Journal of Law, Science and Technology is not to worry about it too much.

The article criticizes the book Genetic Justice: DNA Databanks, Criminal Investigations, and Civil Liberties by Sheldon Krimsky and Tania Simoncelli. The book has latched on to a particular genetic anomaly referred to as chimerism. Chimerism denotes the presence of two genetically distinct cell lines in the human body. The authors of Genetic Justice want to use this rare condition to show that the supposed assumption that DNA profiling is infallible is incorrect.

Think for a moment about what DNA evidence has done in criminal law. Do not just think of the convictions, but think of the acquittals, and think of those freed from incarceration by innocence projects around the country that can be attributed to the use of DNA evidence. To call DNA evidence into question over such a rare and insignificant condition such a chimerism stretches the confines of reasonableness. Genetic Justice proffers that there is a 1/2400, 1/10, 1/8, and 1/1 incidence of chimerism. Other estimates are no better. A 2010 article in the Globe and Mail entitled “The Dark Side of DNA” called DNA evidence into question and offered that chimerism may be present in anywhere from a tiny population to ten percent of the population. If an entire science is going to be called into question some better statistics might be advisable first.

This book and other sources, such as “Expert evidence: the genetic chimerism and its implications for the world of law” by Daniel Bezerra Bevenuto assume that if genetic evidence is gathered and then does not match the defendant’s DNA that the courts and lawyers will simply dismiss the case. I think courts can handle whatever problems chimerism presents. If DNA is recovered at a crime scene and identifies person X and said person is chimeric and the reference sample he provides doesn’t match the sample recovered at the crime scene the court will rightly be concerned. The natural and simple remedy to this solution is just to test again. Normally chimeric cells are isolated so a second reference sample taken from the suspect should resolve the anomaly.

Chimerism does not preset the problem that the authors of Genetic Justice suggest. It is a rare occurrence that a DNA sample recovered at a crime scene doesn’t match the DNA of the suspect it identifies. And even in those rare circumstances where the DNA doesn’t match it is an easy fix. For a more detailed analysis of this issue please read the article by David H. Kaye in the Minnesota Journal of Law Science and Technology.

The full issue of MJLST in which David Kaye’s article appears can be found here.