In this learning object the student will learn how to measure a stain and calculate angles of impact. Determining the angle of impact for bloodstains takes advantage of the trigonometric functions (Sine function).
A mathematical relationship exists between the width and length of an elliptical bloodstain which allows for the calculation of the angle of the impact for the original spherical drop of blood.
Given well formed stains we can accurately measure the width and length by simply dividing the stain along it’s major and minor axis. The opposite halves would be generally equal to each other which aids in establishing the impact angle.
Learners examine OSHA's guidelines of what to include in a bloodborne pathogen exposure control plan for persons who work in general industry, health care, emergency medical services, law enforcement, education, recreation industries, or other occupations in which there is a potential for exposure to blood, blood products, bodily fluids, or human tissues.
Learners view videos of law enforcement and corrections officers describing their jobs and the opportunities in their fields. Because this object contains large video files, it is best viewed using a high band width connection. Low band widths will result in longer download time and video delays.
This screencast, we see how the shape of a stain defines the angle of impact. In general terms the more circular the stain, the more perpendicular will be the angle at which it struck the surface. The more elliptical the shape of the stain, the more acute the angle will be. With practice and experience, the analyst can recognize the general angle of impact based solely on the shape of the stain.