Directional Analysis of Bloodstain Patterns Found at Crime Scenes

Free demo-software for the Directional Analysis of bloodspatter.

Using DNA to identify  bloodstains? The BackTrack™ software enables the analyst to locate the sources of the blood by carrying out a Directional Analysis of the bloodstain patterns.  

 Don't make the mistake of going to court with a bloodstain evidence report that lacks a proper BackTrack ™ analysis of the scene.   

This site also has a description of  Directional Analysis and a discussion of the validity of this ingenious procedure.

Version 3.00 is now available on a CD along with a set of training videos that can be viewed directly on your computer monitor. These video clips show the  monitor screen while Dr Fred Carter runs his programs and demonstrates, with narration, how to use them efficiently.

In addition there is a clip produced with the Tracks program where a bloodstain pattern is created on a vertical surface. The computed flight paths are compared to the 2D convergent lines drawn on the wall, illustrating  how false convergences can result. A valuable lesson for gaining insight into bloodspatter analysis. Tracks will now be distributed along with the BackTrack programs at no extra charge.

The Canadian Society of Forensic Science has recently published a special edition of their Journal that is devoted to Bloodstain Pattern Analysis. (http://www.csfs.ca/journal/journal.htm).One of the articles is my paper "The Directional Analysis of Bloodstain Patterns, Theory and Experimental Validation".

This article can now be referred to by BPAs as published proof that the BackTrack procedure is based on sound science and uses the latest digital imaging techniques with computers. Also it shows that the method is capable of reliable and accurate results.

Bloodstain Pattern Analysts and interested forensic investigators can receive a copy this paper by contacting the author at fredcarter@bloodspattersoftware.com

When the flight paths of the blood droplets have significant curvature, the 2 dimensional convergence  method is only valid on horizontal surfaces (floors, ceilings, etc). It is not valid for vertical surfaces (walls). However, with a 3D Directional Analysis, the errors due to curvature effects appear only in the height of the source location.

More about the Directional Analysis of Bloodstain Patterns:   

Twelve stains were selected from a bloodstain pattern that was produced in the laboratory. A number of screen shots from BackTrack/Win are depicted showing a Directional Analysis of the bloodstain pattern:    

Using BackTrack/Images, stain 10 is analyzed for the impact angle alpha and the directionality angle gamma by fitting an ellipse to the image of the stain. BackTrack/Images produces a data file that can be read by BackTrack/Win.    

The following are Free Demonstration Versions of our software for Blood Spatter Analysis.  

Download into a convenient folder and run these self- installing programs.

• BackTrack^(R)/Win, Version 3.05 (3.1 Mb).This program will enable the blood spatter analyst to carry out a sophisticated Directional Analysis for up to 100 bloodstains located on 12 different surfaces at a crime scene. The data that define the virtual strings to be assigned to the blood stains can be entered via the keyboard or read from a file created by BackTrack/Images. An on line user's manual is included as a help file. Example data files are provided e.g. see "kitchen.bt1" for a pattern of 40 bloodstains in a kitchen. This was an exercise held during the RCMP Math /Physics training course at the Canadian Police College in Ottawa, in March 1997. See also part 3, chapter 2 in "Scientific and Legal Applications of Bloodstain Pattern Interpretation" edited by Stuart H. James for an example of the use of this program.

• BackTrack^(R)/Images, Version 3.05 (2.26 Mb) This program speeds up the analysis by the use of digital images^* of individual bloodstains created by a digital camera or by a camcorder. It offers the blood spatter analyst unprecedented accuracy along with the ease of measurements that is provided by digital photography. An on line user's manual is included as a help file. In addition, there is a tutorial provided by 6 bloodstains from a pattern produced in the laboratory. These stains have correct ellipses fitted for instructional purposes. See also chapter 15 in Forensic Evidence In Canada second edition, edited by G.M. Chako and E.D. Gulliver.

• Tracks^(R), Version 2.22 (1.68 Mb)This program enables the blood spatter analyst to create bloodstain patterns on a vertical surface, by projecting individual blood droplets of varying sizes, speeds and directions towards the surface. The program computes the flight path taking into account air resistance. It also computes the impact parameters such as, the impact angle, the directionality angle, the impact speed and the location of the impact on the wall. It can show the  virtual strings for each stain for comparison with the true flight paths. It comes with example files including "falsecp.trk", which illustrates the false convergence point due to curvature of the flight paths that was discussed in chapter 2, Part 2 in "Scientific and Legal Applications of Bloodstain Pattern Interpretation" edited by Stuart H. James and recently published by CRC Press.

* The use of computers and digital images for blood spatter analysis are unique procedures that were invented and developed, by the author. The software is distributed by Forensic Computing of Ottawa Inc.

Please note the new prices.

E-mail address: fredcarter@bloodspattersoftware.com  

Last revision: June 19 2004