Blood Spatter Interpretation, and how it is used in police investigations.

Flight Characteristics and Stain Patterns of Human Blood : Herbert MacDonnell

Modern American blood-spatter analysis didn’t originate in a crime laboratory, It started decades before the masterful Dexter, of TV fame, in Corning, New York, in Herbert MacDonell’s basement.

MacDonell was a chemist, but he always forensics, and came up with the concept of magnet fingerprint powder, and invented the magnet fingerprint brush. His love for the discipline really took off when he started experimenting with blood drops. He became fascinated on how the reacted in flight, and more importantly, how they reacted when they collided with something, either from gravity or by centrifugal force.

MacDonnell spent countless hours in his basement, which he converted into a home laboratory, where he tirelessly experimented in the dynamics of blood stains in flight, and how they reacted upon striking a different surfaces, and how they reacted when striking objects at an angle. He developed a way to determine the origins of blood spatter by taking examination of the drops at rest.

His basement laboratory experiments started in 1935, when he was only seven years old. In the 1950s, he was pursuing a graduate degree focusing on analytical chemistry, that he got a firsthand taste of real forensics while working in a Rhode Island state crime laboratory. After graduating, he began working at Corning Glass Works as a chemist. He did extensive work there on the development of their casserole dishes.

Away from Corning, he taught forensics at a nearby community college and began moonlighting as a consultant.

In 1968, he really started on the path of leaving the glassware company for full time work in forensics, and as a forensic expert witness.

MacDonell testified for the defense in a New York murder trial where defendant shot a former employee and claimed it was an accident. The prosecution said the victim was sitting in his car when defendant shot him. The defendant said that he did shoot the victim, however he claimed it was an accident, and that the shot was only fired when the victim opened his car door, causing the gun to be struck, in turn, discharging it accidentally.

MacDonell studied the crime scene, and found blood spattered along the inside edge of the car door — an area only exposed when the door was open. MacDonell testified, that the defendant was telling the truth, and the fact of the blood on the inside proved it. s story was true. The jury the suspect guilty, but the case was a revelation for MacDonell

MacDonell had learned that blood spatter interpretation was going to continue to be important to forensics, and he believed, investigators could analyze bloodstains at crime scenes to determine critical evidence such as where the victim was standing during the bloodshed. His experimentation also taught him that different weapons caused different pattern characteristics. He learned that weapons that traveled at significantly different speeds, produced very different patterns. For example, the speed of a swinging baseball bat would produce significantly different patterns than would a bullet.

He documented his work in pages and pages of photographs of blood spattering on different surfaces: neat circles that fell 90 degrees onto a smooth surface, vs the jagged edges produce from the same 90 degree drop would make in rough concrete. He worked on figuring how angles affected the blood droplets.

MacDonell was a scientist, but he believed he could instruct police officers to interpret the dynamics of blood, and he began teaching classes on the subject, turning out scores of newly minted blood-spatter experts.

He then began to teach intermediate and advanced classes for the ones who had the basic classes, teaching advanced courses to students who already passed his basic course.

Graduates of his advanced classes went formed a new professional society — the International Association of Bloodstain Pattern Analysts — in 1983. The following year, IABPA published the first issue of the Journal of Bloodstain Pattern Analysis.

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