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Using Inexpensive Torpedo Lasers to Determine Blood Spatter Points of Convergence

By H.W. “Rus” Ruslander, CSCSA, CLPE, CBPE, D-ABMDI

As a bloodstain pattern examiner, I have used the conventional “stringing” method I learned in the basic blood spatter course taught by Mr. Toby Wolson at the Miami-Dade Police Department. I have also used several other methods, such as mason’s chalk lines, artist tape, drawing a line through the long axis of stains with a straight edge and an overlay of the pattern area using a sheet of clear plastic with lines drawn on it with a marker.

While all these methods work equally well, I have found that using inexpensive torpedo laser levels is an easy, quick and extremely accurate method to use. These small lasers come with a tripod and, most importantly a magnetic cap that converts the laser dot to a straight line! They also have an off-on switch and not a momentary switch. They can be purchased in a variety of hardware stores, department stores or on the internet. Since they are already threaded for 1/4x20 threads, they can be mounted onto conventional tripods instead of using the small tripods that are included with the laser.

The lasers used were “Torpedo Boy” by Opcom. They cost about $10.00 apiece, and are equipped with a bubble level on the top so you can make sure it is level to the floor and perpendicular to the plane of the surface where the blood stains are present.

By setting up a number of these lasers, one can adjust the lines they project, and then align the beams through the long axis of each blood stain to establish a point of convergence. Photographing the results is fairly easy by simply darkening the room somewhat to brighten the projected light and yield photos documenting the point of convergence with remarkable clarity. Example 1 shows an image taken from inside the residence with a Nikon D-70 digital SLR camera of the laser beams projected onto a white metal front door that was standing open at 90 degrees to the door frame at about 3:00 P.M. on a bright sunny day with ambient daylight illuminating the door. While the image is not vibrantly bright, it is viewable. The door in this example swings inward.

Example 2 was taken with the same camera from inside the residence, of the same door, that is now closed. No flash was used and of course, the natural sunlight streaming in through the open door has been eliminated by closing the door. About 4 feet away was a window with outside light streaming through it and across the room was another window providing natural light that illuminated the room from behind.

Use of a flash is not recommended when photographing the display. As with any photography in reduced light, instead of using a flash which would wipe out the laser beams projected on the surface, mounting the camera on a tripod, using a shutter release cable or time delayed trigger and extending the exposure time and/or opening the lens will allow for more image saturation on the CCD or film.

The projected image is very easy to see and use for the establishment of a point of convergence. I have not found any drawback to using this method in normally lit rooms. However, outside in direct sunlight would present a problem. This could be overcome by using tarps or some other materials to shade the area being examined.

Examples 3 and 4 show the laser levels that were used, one with legs extended and one without. Example 5 shows their position on the floor projecting up to the door.

Deciding on the number of stains you use will dictate the number of lasers you need. By using the included tripods, both with legs extended and not, as well as conventional photographic tripods, it is conceivable that as many as 10 or 20 lasers could be used without too much trouble.

Once the point of convergence has been established, it is very easy to then determine the point of origin by using a yard stick mounted on a tripod with either the normal trigonometric calculations of W÷L to find the inverse sin or with the tangent method. An article by Fons Chafe (I.A.B.P.A News, September 2007, pages 4-14) in the most recent edition of the I.A.B.P.A. News details a method utilizing Excel Spreadsheets. This method teaches you how to set up an Excel spreadsheet to input the measurements that will then be calculated to show the area of origin. The only shortfall I see with this method is that it does not, by itself, graphically illustrate the point of origin like the stringing method does. The stringing method provides a good prop for photographic capture and later for display to investigators, prosecutors and judges.

The tangent method can be used to extrapolate the point of origin which can be shown graphically on a computer using any one of a number of drafting or crime scene diagramming programs.

By using the lasers and then placing a yard stick mounted on a tripod at the point of convergence, you can then use the tangent method to determine how far away from the surface the source that the bleeding originated from. It is then very easy to place a marker of some sort on the yard stick at that point to graphically illustrate the general area where the bleeding originated from. This will preclude the need to use actual strings but still provide the graphic image for the viewers.

Another way to determine point of origin would be to use a laser mounted on a protractor. Place the zero point of the protractor at the edge and along the long axis of each stain and project it onto the yard stick. Examples 6 through 10 show how the angle finder laser is used and what it looks like. This will designate the point of origin on the yard stick and where to place the Styrofoam head.

Bear in mind that the actual point or area of origin would be determined by the area(s) of impact to the actual victim. That area would be used as the area of origin. This could require the tripod to be lowered or raised so the area was actually on the same plane as the area of injury the victim sustained.

Examples 11, 12, 13 and 14 show how this was set up for example 1 and how even with bright outside light streaming into the room the laser generated lines are visible in example 1.

By using the tripod, yardstick and a Styrofoam head that I obtained from a wig store, the jury has a readily recognizable image of where the event occurred, and the use of the wig display head adds a “human” touch to the scene. Examples 15 and 16 above show how that would look when set up using the head, lasers, tripod and yard stick. These photographs were taken with just two 60 watt table lamps, illuminating the room. One lamp was about 12 feet to the right of the tripod and the other about 18 feet behind the head and tripod. Both photographs were taken with the camera being handheld, not supported by a tripod! As is evident, sharp, clear pictures are easily obtainable.

One word of caution is needed. Research has shown that in some instances prolonged exposure to the light emitted from lasers could have a negative effect on DNA. I don’t think these lasers emit a strong enough beam of light to have that negative effect. However, as with any investigative process, adequate written, photographic and sample collection methods should be performed prior to any process to document point of origin or convergence.

Using this method is much quicker than any of the other methods I have used in the past. It took me less than 5 minutes to set up the exercise described here. The entire amount of time it took included the time it took to load batteries in the lasers!

While this article refers to the torpedo laser levels, there are other models of lasers on the market that would lend them to this task equally well. One model I have seen is available that can be adjusted both vertically as well as adjusting the projected beam at any angle between 0 and 90 degrees. These are also inexpensive and can cost less than $10.00 as shown in example 17 and 18.

About the author

Harold W. “Rus” Ruslander spent the first 23 years of his career as a Prince George’s County, Maryland Police Officer. That career included uniform patrol, special operations, and administrative and investigative assignments.

After retiring, he moved to south Florida where he became a civilian crime scene investigator first for the City of Lake Worth and then for the Palm Beach County Sheriff’s Office. He is now the Chief Investigator for the Palm Beach County, Florida Medical Examiner’s Office.

Mr. Ruslander’s accomplishments include being certified by the IAI as a Senior Crime Scene Analyst, a Certified Bloodstain Pattern group, Examiner and a Certified Latent Print Examiner as well as by the ABMDI as a Registered Medicolegal Death Investigator. In addition, he is Court recognized as a bloodstain pattern, latent fingerprint and crime scene reconstruction expert. Mr. Ruslander teaches for the Taylor Group, The Gold Coast Forensic Association, The I.A.I., the F.D.I.A.I, and the Tri-State Division of the IAI and has designed numerous different workshops. The Florida Department of Law Enforcement also certifies him as a law enforcement instructor.

Mr. Ruslander has written over 20 forensic articles, which have been published in a number of forensic publications and various sites on the worldwide web. Mr. Ruslander has also made presentations and taught courses for the IAI annual training conferences, the FDIAI Annual Training Conferences, The East Coast Armed Robbery Association, The Taylor Group, The Gold Coast Forensic Association, the Florida Chaplains Association and the Florida Fire Marshals Association.

Mr. Ruslander is a member of the IAI, FDIAI, ABMDI, IABPA, Gold Coast Forensic Assn. and CBDIAI, past president of the FDIAI, vice president of the Gold Coast Forensic Association and a member of the IAI Board of Directors.

Copyright 2011 - Richard Warrington
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