Several well-known criminal cases have turned on blood spatter analysis, and together they tell a mixed story about the discipline. Sam Sheppard’s 1966 acquittal, O.J. Simpson’s 1995 verdict, and the exonerations of David Camm and Joe Bryan all hinged on how experts read blood at a crime scene. Some of those readings held up; others collapsed under scrutiny after the defendant had already spent decades in prison.
Bloodstain pattern analysts study the size, shape, and distribution of stains to work out where blood came from, what direction it traveled, and what force produced the pattern. A drop falling straight down looks nothing like the fine mist a gunshot creates or the arc thrown from a swinging weapon. The main categories are passive stains from gravity, impact spatter from a blow to a blood source, cast-off patterns from a moving object, transfer stains from contact, and arterial spurts with their wave-like edges. Those distinctions sound clean on paper. In practice, qualified analysts often disagree about which category a given stain belongs to, and that disagreement is where the courtroom trouble starts.
Sam Sheppard, 1954: Blood Evidence Enters American Courtrooms
On July 4, 1954, Marilyn Sheppard was found beaten to death in her Bay Village, Ohio, home. She was four months pregnant. Her husband, Dr. Sam Sheppard, told police a bushy-haired intruder had attacked him and killed his wife. Investigators didn’t believe him, and after a nine-week trial dominated by press coverage he was convicted of second-degree murder in December 1954 and sentenced to life.
The case’s lasting importance for forensic science came on appeal. Dr. Paul Kirk, a criminologist from the University of California, conducted an independent blood spatter analysis and reached conclusions that cut against the prosecution. The blood patterns radiating from the victim’s head, he found, indicated a left-handed killer. Sheppard was right-handed. Kirk also identified a large bloodstain on a wardrobe door that matched neither Marilyn nor Sam, suggesting a third person had been present and injured.
The U.S. Supreme Court reversed the conviction in 1966 on the ground of prejudicial pretrial publicity rather than on the blood evidence. But at the retrial, spatter analysis took the lead. Prosecution witnesses said spots on Sheppard’s watch were spatter that could only have gotten there if he committed the murder. Defense experts said the marks were contact transfer, not flying blood. The jury acquitted. It was one of the first American trials to present juries with directly opposed readings of the same bloodstains, and it set a template the field has never really escaped.
O.J. Simpson, 1995: Dueling Experts on National Television
Nicole Brown Simpson and Ronald Goldman were stabbed to death on June 12, 1994. Blood evidence connecting O.J. Simpson to the scene became one of the most contested parts of the case. DNA testing showed that blood on socks found in Simpson’s bedroom closely matched Nicole Simpson’s genetic profile, and a bloody glove recovered behind his estate became a signature piece of physical evidence.
Herbert MacDonell, a pioneer in bloodstain analysis, testified for the defense about the socks. Examining the stains under a stereo-microscope, he concluded the blood had been pressed into the fabric through direct contact rather than deposited by violent action, and that it had soaked through from one side to the other. That reading supported the defense argument that the blood had been placed on the socks after they were collected.
Dr. Henry Lee also testified for the defense. He walked the jury through the basics of pattern analysis using red ink on white paper, then pointed to tiny spherical drops on the socks as further support for the planting theory. Prosecutors maintained that the patterns around the victims were consistent with a single attacker matching Simpson’s physical profile. The jury acquitted. The trial reached a national audience with an unmistakable lesson: two credentialed analysts can look at the same blood and describe two different crimes.
David Camm, 2000: Thirteen Years Lost to an Unqualified Analyst
On September 28, 2000, David Camm, a former Indiana State Trooper, came home to find his wife shot dead on the garage floor and his two children dead in the family vehicle. He pulled his son from the car and attempted CPR, then called the Indiana State Police.
The Floyd County prosecutor hired an Oregon-based forensics firm, and the work went to Robert Stites, a forensic assistant. Stites told investigators that stains on Camm’s T-shirt were “high-velocity impact spatter,” a pattern associated with the presence of a gunshot. That meant, in his telling, that Camm had been standing next to the victims when they were shot. Police arrested Camm two days later, relying almost entirely on that reading.
At trial, Stites testified that he was a crime scene reconstructionist working on advanced degrees in fluid dynamics and that he had investigated homicides for the Army, Naval Intelligence, and the FBI. None of it was true. His only degree was in economics. He had never taken a course in fluid dynamics and had failed his one college chemistry class. He had never processed a homicide scene before Camm’s. The prosecutor had walked him through the scientific method before trial.
His analytical errors matched his fabricated résumé. He labeled high-velocity impact spatter on the garage door, shower curtains, siding, a mop, and a jacket. Only the stain on the T-shirt was actually blood. He also claimed the blood’s viscosity showed a chemical cleanup, when the appearance was serum separation, a natural process he had never seen because he had never examined fresh blood at a scene.
Camm was convicted, then had the conviction overturned, then was convicted again at a second trial. At his third trial in 2013, defense experts testified that the eight specks on his shirt were transfer stains left when he pulled his son from the car. After eight weeks and 88 witnesses, the jury acquitted him. He had spent thirteen years in prison. The Seventh Circuit later described the original arrest warrant as based on “a plainly unqualified forensic assistant who was not trained to do anything more than photograph evidence.”
Joe Bryan, 1986: Forty Hours of Training, Thirty-Three Years in Prison
Joe Bryan, a high school principal in Clifton, Texas, was convicted in 1986 of murdering his wife largely on the testimony of Robert Thorman, a police detective who took the stand as a bloodstain pattern expert. Thorman told the jury that blood flecks on a flashlight recovered from Bryan’s car were “back spatter” from a close-range gunshot, and that the killer had held the flashlight in one hand while firing with the other. His entire training in the field amounted to forty hours.
Decades later, in July 2018, the Texas Forensic Science Commission reviewed the blood evidence and found Thorman’s analysis “not accurate or scientifically supported.” Two months after that, Thorman himself signed an affidavit conceding the point: “My conclusions were wrong. Some of the techniques and methodology were incorrect. Therefore, some of my testimony was not correct.” When the Texas Department of Public Safety Crime Lab finally tested the flashlight, five of six tested stains came back negative for blood entirely. A partial DNA profile from the lens was inconclusive.
Bryan was released on parole in 2020 after thirty-three years. His legal team has continued to pursue full exoneration in federal court.
Warren Horinek and Brad Jennings
The same pattern repeats in smaller cases. Warren Horinek, a Texas man convicted of murdering his wife, was found guilty in part because prosecution expert Tom Bevel testified that blood spots on his shirt were gunshot spatter. Multiple nationally recognized analysts later examined the same evidence and said the spots were consistent with Horinek administering CPR. His conviction was affirmed on appeal and remains disputed within the field.
Brad Jennings, a Missouri man convicted in 2006 of killing his wife, had his conviction vacated after evidence emerged supporting his claim that his wife had committed suicide. Blood spatter testimony was part of the prosecution’s case.
Each of these cases has the same shape. A prosecution analyst sees gunshot spatter. A defense analyst, sometimes years later, sees CPR transfer or something else entirely. Both are confident. The jury, with no independent way to test the science, has to pick an expert to trust.
What the Science Actually Shows
Two major government-commissioned reviews have looked at the reliability of bloodstain pattern analysis, and neither offered much reassurance. The 2009 National Academy of Sciences report, Strengthening Forensic Science in the United States: A Path Forward, concluded that “the opinions of bloodstain pattern analysts are more subjective than scientific” and that “the uncertainties associated with bloodstain pattern analysis are enormous.”1Office of Justice Programs. Strengthening Forensic Science in the United States: A Path Forward The report acknowledged that science supports some basic aspects of the discipline, such as distinguishing fast-moving from slow-moving blood, but said some practitioners “extrapolate far beyond what can be supported.”
The panel also flagged structural problems. The International Association for Identification, a major certifying body, had no educational requirements for certification in bloodstain pattern analysis. The report called the field’s emphasis on experience over scientific foundations “misguided, given the importance of rigorous and objective hypothesis testing and the complex nature of fluid dynamics,” and noted that casework is often “prosecution driven or defense driven, with targeted requests that can lead to context bias.”1Office of Justice Programs. Strengthening Forensic Science in the United States: A Path Forward
The 2016 President’s Council of Advisors on Science and Technology (PCAST) report echoed those concerns and called for well-designed error rate studies and objective, quantitative methods across forensic disciplines, including blood pattern analysis. Research done in response found that analysts’ conclusions were wrong roughly 11 percent of the time, and any two analysts examining the same evidence contradicted each other about 8 percent of the time. When an analyst made an error, a second analyst reproduced that same error 18 to 34 percent of the time. Researchers linked the variability in part to inconsistent terminology and classification standards across the field.2National Institute of Justice. Study Reports Error Rates for Bloodstain Pattern Analysis
How Courts Handle Blood Spatter Testimony Today
Federal courts and most state courts assess whether to admit expert testimony under the framework from Daubert v. Merrell Dow Pharmaceuticals (1993). The Supreme Court identified several factors for a trial judge: whether the method has been tested, whether it has been through peer review and publication, its known or potential error rate, and whether it enjoys widespread acceptance in the relevant scientific community.3Justia. Daubert v. Merrell Dow Pharmaceuticals, Inc. These are considerations rather than a checklist, and they apply to the methodology rather than to the expert’s specific conclusions.
Federal Rule of Evidence 702, amended most recently in December 2023, codifies this gatekeeping role. The rule requires the party offering the expert to show it is “more likely than not” that the testimony will help the jury, that it rests on sufficient facts, that it uses reliable methods, and that those methods have been applied reliably to the case at hand.4Legal Information Institute. Federal Rules of Evidence Rule 702 – Testimony by Expert Witnesses The 2023 amendment was aimed at courts that had been treating fundamental methodological questions as issues of weight for the jury rather than admissibility questions for the judge.
Despite the NAS and PCAST criticisms, bloodstain pattern testimony continues to be admitted routinely. Judges have wide discretion under Daubert, and challenging one analyst’s qualifications rarely bars the whole discipline. Camm’s case sits at the extreme end of what happens when gatekeeping fails outright; Stites would almost certainly never have been allowed to testify had the judge known who he was. In cases involving genuinely qualified analysts, courts generally leave the dispute for the jury to resolve, which is precisely how you get the outcome Sheppard, Simpson, and Bryan have in common: the verdict comes down to which expert the jury believed.