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Evidence Written in Blood: Forensic Science and the True Crime Consumer

Evidence Written in Blood: Forensic Science and the True Crime Consumer

According to reports, in December 2001 Michael Peterson found his wife, Kathleen Peterson, dead at the bottom of a set of stairs in their Durham home. While locals like me remember the hullabaloo that followed, true crime fans became familiar with the case through a multipart French documentary, The Staircase, which Netflix renewed for five episodes last year. Before its resurgence into popular memory, however, another important purveyor of true crime told the Petersons’s story in 2006: Forensic Files.

Netflix’s The Staircase charts the murder trial of Kathleen Peterson and subsequent questions about blood spatter analysis. (Courtesy Netflix)

In the episode, viewers heard from several experts, the most important being blood-spatter analyst Duane Deaver. The audience watched Deaver test Michael Peterson’s clothing, including the blood- and water-soaked shorts he was wearing the night of his wife’s death. “His experience and training,” the narrator explained, led Deaver to look between the legs of the shorts, where he found spatter untainted by water.1 “That is something I see many times in beating cases,” Deaver told the audience, “because generally when you’re standing over a victim and you’re beating them, a lot of the impact spatter will come directly back on the individual and will go into the crotch area.”2 As shown on screen, Deaver then conducted a test to reproduce the spatter by beating a paint-soaked sponge with a blunt object until flecks of paint landed on the inside of his own shorts. “The individual wearing those shorts,” he concluded, “had most likely been standing over someone as they beat them,” and the pattern could not have resulted from an accidental death.3 Largely as a result of Deaver’s testimony, the state convicted Michael Peterson of his wife’s murder in 2003. In the final moments of the special, author Diane Fanning declared that science clinched the case: “The forensic evidence in this case was written in Kathleen Peterson’s blood and the people that processed that scene did the job that needed to be done to put a guilty person behind bars.”4

If you’ve seen The Staircase, however, you know the story does not end there. The state released Michael Peterson on bond in 2011 and he entered an Alford plea in 2017. The “job that needed to be done” to put him away, it turns out, may have been fabricating blood evidence. The State Bureau of Investigation fired Deaver in 2011 after finding that he had conducted bogus tests and misreported evidence in as many as two hundred cases, including one that led to a wrongful conviction in 1993.

For many, though, this revelation hardly matters. True crime fans in my hometown of Durham and elsewhere continue to insist upon Michael Peterson’s guilt for one major reason: How else do you explain the blood?

Forensic Science on TV

“Forensic science” simply refers to the application of scientific methods to the criminal law and can encompass a range of procedures, though many of us are most familiar with blood testing. In a striking parallel to the Peterson case, one of the earliest uses of blood spatter analysis determined that a woman found at the bottom of a staircase had been the victim of “a murderous assault” during the 1840s.5 Science has been a part of criminal investigation for thousands of years, but forensics began to rapidly professionalize in the United States when J. Edgar Hoover opened the first federal crime lab for blood-alcohol testing during Prohibition.6 The lab later became a part of the FBI, developing training programs for law enforcement agencies across the country. While the general public has been fascinated by crime science since at least the dawn of popular detective fiction, technical knowledge of forensics — or the illusion of it — remained the purview of professionals until the late twentieth century.

Forensic Files, originally titled Medical Detectives, first aired in 1996 and was one in a long line of true crime shows that gained popularity after the 1970s. Unsolved Mysteries, America’s Most Wanted, Dateline, and others exploded onto cable television during the late ‘80s and ‘90s, offering Americans a window into the world of real life crime-solving. The same era brought unprecedented coverage of high-profile criminal trials, like those of OJ Simpson and the Menendez brothers, into homes across the country. As true crime evolved, so did its attention to what types of evidence most appealed to jurors. Forensic Files reflected a shift toward a popular interest in scientifically evaluable physical evidence and an effort on the part of networks like Court TV to educate viewers on the technical aspects of criminal investigation.

What made shows like Forensic Files different from procedural dramas like Quincy, ME, and CSI was their unwavering claim to the truth through the seemingly neutral force of the science performed in real investigations. Stakes were high for catching the criminal in these 22-minute episodes, as eerie music played over flashes of grisly crime scene photos and violent reenactments. The narrator explained complex forensic processes while scientists demonstrated tests on camera. As a result, technical terms like “luminol,” “high velocity impact spatter,” and “blunt force trauma” have become a part of the everyday lexicon of true crime fans. While Forensic Files’s focus on real science lent it an air of objectivity, most episodes slanted toward the prosecution, featuring commentary from police, prosecutors, and witnesses, who spoke to the importance of physical evidence for putting bad guys away.

At-Home “Experts”

True crime pushed for the infallibility of forensics both on and off-screen, creating lasting effects on Americans’ perception of the justice system and the individual consumer’s belief in their own capacity to solve crime. The genre is often interactive and communicates to consumers that they are qualified to form opinions about cases based on their own evaluation of the evidence. Crime museums further this illusion of expertise with hands-on exhibits where guests can test their knowledge by matching dental records, testing fingerprints, doing ballistics analysis, and identifying types of bodily wounds associated with certain weapons, while gift shops sell mock fingerprinting kits for children.7 At this year’s biggest true crime convention, Crime Con, fans paid between $300 and $1500 for access to sessions like “The DNA of Murder” with celebrity detective Paul Holes, who walked through a staged crime scene soliciting audience input on blood spatter to determine a possible motive and murder weapon. Because of such popular interest, attorneys argue that witnesses have had to get more creative to appeal to juries who now anticipate an unattainable level of scientific evidence in every trial.8

Visitors to the Vancouver Police Museum participate in a demonstration of blood spatter analysis. (Courtesy John Biehler)

Unfortunately, since the ‘80s, these true crime products have also presented skewed information about what forensic science actually entails. According to one expert at Crime Con, most labs do not even test for gunshot residue and trace evidence, or conduct blood spatter analysis, despite their ubiquity in shows like Forensic Files. These methods, he explained, leave too much room for error.9 The audience gasped at the news. One woman a few rows ahead of me whispered to her neighbor: “I’m sorry, I just don’t believe that.”

This refusal to believe in the potential flaws of scientific testing has led to a larger inability to scrutinize the use of physical evidence in securing convictions, and public perception is especially important since members of the public serve on juries. While sensational cases like Michael Peterson’s can illustrate the dangers of bad science, marginalized people and those accused of petty crimes have been incarcerated on the basis of faulty evidence much more often. As recently as 2007, mismanagement and clerical error called into question between 5,000 and 10,000 DNA tests conducted at a lab in Houston, Texas.10 Many of them produced convictions. After an investigation, the lab began to operate independently from the city of Houston, but most crime labs in the US have always and still do report to police departments. Police want answers fast, which means that, historically, they have cared less about the accuracy of tests than about implicating a suspect.11 This conflict of interest helps to explain why Forensic Files episodes fail to interview suspects or members of the defense: the narrative of foolproof science best serves those with the power to convict and incarcerate.

True crime stories provide a sense of order in a disorderly world and consumers, influenced by forty years of them, hold fast to the belief that forensic knowledge will prevail in the face of uncertainty.12 After studying the crime scene photos in The Staircase, one friend told me that she had “seen too much Forensic Files” to believe Kathleen Peterson’s death was an accident. As a historian (even one from Durham!) it is not my responsibility to determine whether it was, but it is every true crime consumer’s responsibility to question evidence with the potential to wrongfully convict — especially evidence presented on TV shows that have argued since the 1980s that science never lies.


  1. Forensic Files, “A Novel Idea,” season 11, episode 22, aired December 13, 2006, on TLC Network, 12:45. Return to text.
  2. “A Novel Idea,” 12:50. Return to text.
  3. “A Novel Idea,” 13:00. Return to text.
  4. “A Novel Idea,” 20:30. Return to text.
  5. Suzanne Bell, Crime and Circumstance: The History of Forensic Science (Westport, CT: Praeger, 2008), 213. Return to text.
  6. Bell, Crime and Circumstance, 197. Return to text.
  7. While the original National Museum of Crime and Punishment closed in 2015, much of its collection is now housed at Alcatraz East Crime Museum in Pigeon Forge, Tennessee. The forensics room is still a part of the permanent exhibit. Return to text.
  8. See Michelle Byers and Val Marie Johnson, eds., The CSI Effect: Television, Crime, and Governance (Lanham, Md.: Lexington Books, 2009). Return to text.
  9. Peter Stout, “Forensics 101” (lecture, Crime Con, New Orleans, LA, June 9, 2019). Return to text.
  10. See the full 2007 report on the Independent Investigation of Houston Police Department Crime Lab: Michael R. Bromwich, Final Report of the Independent Investigator for the Houston Police Department Crime Laboratory and Property Room, June 13, 2007. See also Adam Liptak and Ralph Blumenthal, “New Doubt Cast on Testing in Houston Police Crime Lab,” The New York Times, August 5, 2004. Return to text.
  11. Peter Stout, “Forensics 101.” Return to text.
  12. See Jean Murley, The Rise of True Crime: 20th Century Murder and American Popular Culture (Westport, Conn.: Praeger, 2008). Return to text.

Alyssa Smith is a doctoral candidate at the University of Chicago. She is a historian of 20th-century US culture; violence; crime; social movements; race and racism; gender and sexuality; emotion; and historical memory. Her research focuses on how the fear of violent crime influenced American life during the 1970s, ‘80s, and ‘90s.