Blood Stain Evidence in Criminal Cases: People v. O.J. Simpson
This paper will discuss various aspects of blood stain evidence, particularly with regard to the O.J. Simpson case. The first part of the paper will discuss the interpretation of blood spatter evidence in general. The second part of the paper will look at the Simpson case with regard to such interpretation.
The analysis of blood stain and blood spatter evidence is quite distinct from that of the blood itself. While blood analysis looks at the chemical and DNA characteristics of blood samples taken as evidence, blood stain and blood spatter analysis examines the patterns of the blood found at the crime scene. Blood sample testing is used to identify the persons at the crime scene; blood stain/spatter evidence is used to explain the sequence of events which took place and the manner in which the criminal act was committed.
Analysis of blood spatter has essentially evolved since the 1930s, when French researchers began systematically classifying blood stains based upon their shapes and began studying blood drops through the use of high-speed photography. In 1971, Professor Herbert MacDonell published the seminal work in this area, Flight Characteristics and Stain Patterns of Human Blood. This work has since become the basis of all blood spatter analysis and is still the most complete work on the subject. Ironically, Dr. MacDonell was an expert witness for the defense in the Simpson trial.
The flight characteristics of blood can be accurately predicted by the law of ballistics, whether the blood drips from an object or spatters from the impact of a blow. Through the conduct of experiments using human blood under controlled circumstances, a few predictions can be made. First, the distance between the target surface and the source of the blood at the time the blood dripped is determinable with some accuracy. Second, the point of origin of the blood ca...