Computerized Bloodstain Spatter Analysis

Critical bloodstain evidence that might not have been fully analyzed in the past now can be analyzed thanks to the speed and tenacity of the computer.

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.

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