Computerized Bloodstain Spatter Analysis

Computers are affecting every phase of our lives these days. The real value of the computer comes when there are tasks which require a large number similar operations or calculations. These tasks are tedious which when performed manually and require a great deal of manpower and effort. The untiring computer relentlessly performs these tasks and provide data which otherwise might not be obtained because of the time required.

Computers aid the laboratory

Computers have found their way into a variety of areas in the forensic laboratory and the crime scene investigation process. One such area is bloodstain spatter analysis. The pattern of bloodstains at a crime scene can provide valuable evidence about the events that have occurred. It can determine whether the perpetrator was right- or left-handed, if there was more than one perpetrator involved, and in many cases the order in which the wounds inflicted on the victim occurred. Bloodstain may be present on ceilings, walls, floors and even furniture. It may also be present in more the one room. In addition, the number of bloodstains may be very large and the total number of blood drops within all stains may number into the hundreds or thousands.

The collection of data in this case requires many hours of CSI technicians' time, including photographing bloodstains, measuring and calculation the direction, angle and velocity of individual blood droplets within each bloodstain area. In many cases, sections of walls or flooring may have to be removed and secured as evidence. The technicians try to establish the angle and direction of the blood and from this the position of both victim and perp. The use of colored strings or plastic rods allows these results to be visualized. However, this requires a great amount of work and well-trained people to complete the analysis. The data collected then must be returned to the forensic lab and a large number of calculations made to develop a picture of the events at the crime scene.

Presenting Crime Scene Data

Presentation of crime scene data in the courtroom is essential to convince a judge and jury of the guilt of a suspect. Photographs, diagrams, and courtroom reenactments are all valuable tools, but do not give the jury the sense of being present at the actual crime scene. Computer technology has become a critical ally of the forensic laboratory. The power of the computer to take large amounts of data and convert it into understandable results is reducing the time and the manpower required to analyze complex crime scenes. A number of software programs are available which allow technicians to create a 2D model of the scene and then convert this into a 3D model. Programs are available to allow animation of a crime scene model to how a perpetrator may have moved through the scene and committed the crime.

3D imagery adds a lot

Programs like Crime Zone (CAD Zone, Beaverton, Ore) or iWitness (DeChant Consulting Service, Bellevue, WA.) can take data and create 3D models which can be manipulated to present different views of the scene. The iWitness program analyzes digital pictures of a scene that are taken from three different views but with some features common to each, and then converts this into a series of 3D coordinates that can be used to create a 3D picture. The picture must be created from these coordinate points using a computer-aided drawing (CAD) software program. Crime Zone is one such program which takes the digital image data and creates a 3D image. Crime Zone can also take measurements obtained by a laser measuring device and create a realistic 3D image of the crime scene.

Other systems allow a 3D panoramic image of the entire crime scene to be developed. The viewer is able to scan left or right to see particular aspects of the scene. In addition, the viewer can zoom into the scene and look at any particular aspect of the image. These systems use a special lens on a digital camera which is mounted on a tripod located in the center of the scene. One of these type systems is SpheroCam HDR (Linear Systems, San Bernadino, CA.), which can also create a virtual reality walk-through of the scene by combining images of various hot spots identified by the viewer. PanoScan Corporation (Van Nuys, CA.) creates panoramic images that can be printed out as a photograph or shown on a screen in the courtroom.

Toward virtual reality

These systems, while capable of showing where bloodstain spatter is, are not capable of analyzing this data and providing insight as to how the blood spatter was created. A Durham, NC company, 3rd Tech, has created a 3D capture system that allows bloodstain spatter patterns not only to be captured, but also viewed and analyzed. The DeltaSphere-3000 3D Scanner consists of a laser rangefinder and camera integrated with an embedded computer controller and graphics software. Unlike other camera systems which take a single or small number of pictures (measurements), the DeltaSphere-3000 takes thousands of measurements in a relatively short time. Every point on which the laser is focused is recorded. This means that a particular bloodstain spatter pattern of a kitchen wall consisting of a hundred unique blood spots can be measured from a specific reference point (the camera), and then the distance and angle of impact from the victim can be calculated in a relatively short period of time. This would be like a CSI technician measuring each unique blood spot with a tape measure or trajectory rods thousands of times. This process is then repeated for each bloodstain spatter pattern on the walls, floor or ceiling of the crime scene. Pictures of the bloodstain areas and the related measurement data all are preserved in the computer databank.

This system also allows the scene to be viewed from perspectives such as from above, or from another room. A major advantage of the system is it allows the viewer to see the scene as the victim saw it, then as the perpetrator saw it, or as the first officers on the scene might have seen it. These views can give both investigators and jury members a real feel for being at the scene as the events unfolded.

Watch for Sticker Shock

The price range for these systems runs from around $1000 for the software packages to as much as $50,000 for the laser or high resolution camera 3D systems. While these prices are hard to justify for many departments, these systems can also be used for mapping at crash and traffic related scenes. It may be possible for a department to obtain grant money for technology equipment purchases from the National Highway Traffic Safety Administration. (See related story by Bob Galvin, Mapping choices abound as traffic and crashes mount, Law Enforcement Technology, August 2007).

The ability to see a crime scene from various angles and perspectives and to rapidly process the bloodstain pattern data can provide investigators with valuable information that otherwise would not be available for a period of days or weeks and in many cases might not be available at all because of time and priority constraints.