According to one interpretation of the "barking dog" witnesses, the Bundy victims were dead and the killers were gone by 10:15 at the latest. But, Aaronson and Mandel testified that they passed the scene ten minutes after this, and they did not see any indication that the murders had been committed at that time. Among the indications they did not see was a pattern of bloody dog paw prints on the sidewalk. This article explores the experience they would have had if they passed Nicoles condo when there were fresh paw print on the sidewalk over which they passed.
THE SITUATION. The couples path would have coincided with the dogs track for about 150 feet, from Nicoles walk, south to the corner of Dorothy Street. At that point, the paw prints turned west on Dorothy, but Arronson and Mandel continued to walk south on Bundy. At a normal walking speed, the young couple would have been in a position to see the paw prints for only 30 to 40 seconds. At that time, the area was illuminated only by a sodium vapor street light on the north-east corner of Bundy and Dorothy. At the point where they would first pass over the paw prints, the couple would have been about 200 feet from the street light; when they left the paw prints they would have been about 70 feet from it.
The sodium vapor street light gives off a colored light that has been variously described as a hue of "orange" to "pink." I here refer to it as a "pink light." One of the problems in seeing the paw prints in blood is that the red color of the blood is not illuminated much differently by the street light than the concrete upon which they are imprinted. The combination of low light level, short exposure time, and poor color contrast can be expected to have made it difficult to see the paw prints if they were present.
THE EXPERIMENT: The most difficult of the factors for the analyst to evaluate is the effect of pink light on the recognizability of the paw prints. To test this, I put blood on a white card, and photographed it in daylight and also at night in a place that was only illuminated by a mercury vapor street light. The night photograph was done with the paper target on a concrete surface, so that a sample of concrete illuminated by pink light was also captured. (It is no longer possible to recreate the original situation by putting fresh blood on the sidewalk in front of Nicoles former condo and photographing it. The city of L.A. has since put a street light directly in front of the condo, and the lighting now is entirely different.)
Specifically, a blood stain about 1/2" high by 1-1/2" long was created at 3:00 oclock in the afternoon, and was photographed in sunlight about 3:15 pm. After it was dark, this sample was taken to a point about 10
feet from directly beneath a sodium vapor street light and photographed
at 6:15 pm. (This was done in an alley, so there were no extraneous sources of light.)
The photographs were printed and the prints scanned, then the scans were adjusted with Photoshop to give the same appearance as was seen with the eye at the time the photographs were taken. (The "as printed" representation was considered to be representative of the original image in the alley with regard to color and contrast, but was somewhat brighter because of the camera settings used to get the pictures. No effort was made to adjust the brightness to match the Bundy conditions.)
A composite image was created with the daytime photo on the left, and the pink light photo on the right. For the pink light image, the blood stain on paper was lifted and dropped on a concrete background. This is considered to simulate the situation that Aaronson and Mandel saw.
RESULTS: The result is shown in the accompanying figure. It obvious that the image in daylight is conspicuous, and would be recognized by most people as a fresh blood stain. The same stain on concrete under sodium vapor light is of much lower contrast, and could be overlooked by
one who was not aware that there was something to be seen. More important, the color is not the bright red seen in sunlight, but is considerably browned. As a result, even if it was seen, it is not clear that this is a fresh blood stain, it looks much like a stain that could be a week or two old. If one finds himself walking in a place where there are "old stains," he is not likely to get too excited.
Overall, the following factors limit the recognizability of the bloody paw prints for Aaronson and Mandel who passed the scene with only the ambient light:
The couple was only in a position to see the paw prints for 30 to 40 seconds.
There could have been other stains or debris on the sidewalk with which these stains could have been confused. (It was a time of year when the jacaranda trees were littering the sidewalks in that neighborhood with fallen blossoms, and a year in which debris from earthquake repairs was often piled in gutters and scattered on the sidewalks.)
In the street light, blood on concrete is a low contrast image.
The color would have been brownish, and appeared "old."
At the beginning of the trail, the couple was 200 feet from the street light and the illumination was poor.
At the end of the trail, the lighting was better, but the prints were becoming weak and indistinct.
When these factors are combined with the fact that the couple was not specifically looking for the stains, and had other things on their minds, I believe that it should be expected that they would not notice the bloody paw prints if they were present.
Dick Wagner Van Nuys, CA (12/22/98) NG_497