The researchers measured the size of bloodstains formed by releasing drops of pig's blood (drop diameters 3.0-4.3 mm, velocities 2.4-4.9 m/s) onto a variety of surfaces (steel, glass, plastic laminate, and paper). They then counted the number of spines around each bloodstain and confirmed the validity of using analytical models to predict stain diameter and number of spines. Equations were developed to predict drop velocity and size. The study determined that the maximum stain diameter and number of spines increased with impact velocity and drop diameter. Increasing surface roughness reduced stain diameter and promoted merging of spines, reducing their number. Analytical models were used to obtain simple equations that explicitly related drop diameter and impact velocity to measurements of stain diameter and number of spines. Errors in predicted values were largely due to variations in surface properties. The accuracy of calculations could be improved for a specific surface by observing the size of bloodstains and number of spines on that surface. Additional studies are recommended before applying this method in casework. 4 tables, 14 figures, and 17 references