Forensic Blood Drop Analysis

Blood drop analysis, known in forensics as bloodstain pattern analysis (BPA), is a specialty that applies physics, chemistry, geometry and biology to the blood evidence at a crime scene. Using BPA, investigators and first responders can understand what happened, or did not happen, at a crime scene.

History

Blood drop analysis goes back at least to the 16th century. In 1895, Dr. Eduard Piotrowski at the Institute for Forensic Medicine in Krakow, Poland, published the first scientific study of bloodstain patterns. In 1955, Dr. Paul Kirk testified regarding the bloodstain evidence in the case of the State of Ohio vs. Samuel Sheppard, marking a milestone in the use of BPA in the American legal system. In 1973, Herbert L. MacDonell created a training program for BPA, and in 1983 he helped form the International Association of Bloodstain Pattern Analysts, the foremost organization for experts in the field.

Significance

According to the Scientific Working Group on Bloodstain Pattern Analysis and the International Association of Bloodstain Pattern Analysts, BPA provides a scientific method, guidelines, protocols and techniques for reconstructing and analyzing a crime scene.

Facts

BPA examines the size and shape of blood drops; the quantity of blood and the patterns it forms; the angle at which the drops fall on a surface; and the point where several drops converge. BPA then classifies blood drops as either passive (pooled blood), projected (from a gunshot or blunt force), or non-projected (transferred from another source).

Function

Bloodstain pattern analysis can reveal the type of weapon used; how many blows or shots the victim received; where the victim and assailant were positioned during and after the attack; whether the evidence supports the coroner's findings; and whether the blood at the scene matches any blood found on a suspect.

Considerations

Bloodstain pattern analysis is not 100 percent accurate and will be only as good as the quality of the evidence and the training and expertise of the analyst.

References

• International Association of Bloodstain Pattern Analysts
• FBI Scientific Working Group on Bloodstain Pattern Analysis