Forensics - car and pedestrian

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Discussion Overview

The discussion revolves around a forensic analysis of a car-pedestrian accident depicted in photographs. Participants explore the speed of the vehicle at the time of impact and the potential outcomes for the pedestrian involved. The conversation includes considerations of human reaction times, vehicle specifications, and the interpretation of visual data from the images.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests estimating the car's speed based on the distance traveled as indicated by the dotted lines in the photograph, but acknowledges uncertainty regarding the accuracy of this method.
  • Another participant proposes that the vehicle is a Mercedes Benz C-class wagon, providing its approximate weight.
  • Concerns are raised about the reliability of crude time estimates, with a participant suggesting a wide range for the car's speed based on an initial estimate.
  • Participants discuss the potential for further investigation into the time stamps or other data present in the photographs to obtain a more accurate time lapse.
  • One participant describes the victim's motion during the impact, suggesting a rotation and the sequence of body parts that were struck by the vehicle.
  • Another participant claims that determining the average speed is straightforward by measuring the car's length in the images and calculating distance traveled, while also providing a specific time interval for the event.
  • There is a mention of the pedestrian sustaining a significant head injury based on the condition of the windshield.

Areas of Agreement / Disagreement

Participants express differing views on the methods for estimating speed and time, and there is no consensus on the accuracy of the proposed calculations or the implications for the pedestrian's survival. The discussion remains unresolved regarding the exact circumstances of the accident.

Contextual Notes

Participants note limitations in the available data, including the need for clearer definitions of the figures in the photographs and the potential influence of external factors on the analysis.

Fred_tuber
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I was recently forwarded a link that shows two black&white pictures of an horrible accident - a pedestrian getting thrown in the air by a car. You can click on the link (bottom of message, below), to see the pictures.

Note: although the image is not gorey, it may be disturbing to some. Please exercise discretion before clicking the link.

So, my question is one of forensics: how fast was the car going when the driver blew through the red light, and what is the likelihood that the pedestrian survived?

As far as change in time goes, I cannot interpret the numbers across the top of the photograph. As best I can make out, the offending vehicle traveled from the first set of dotted lines to the third set of lines (thus giving change in distance), which corresponds with the time it took for the pedestrian on the far left to partially complete her step and recoil aghast, which may correspond with the position of the windshield wiper blade on the offending vehicle. This may not be an accurate presumption b/c the victim may have grabbed on to the wiper blade; also, none of the other cars have their wipers on (which does not preclude that our less-than-observant offender could have had the wiper on). Either an appraisal of the human stride and reaction time and/or the average speed of 1/2 cycle of a Mercedes Benz wiper blade would provide an estimate of the time...right?

It looks like the car hit the pedestrian such that his left leg completely buckled and continued to apply force at an angle such that he "glanced off" the hood, hitting his head as the car continued to pass. What would be the force of impact on his head? Did his abdomen suffer trauma, too?

How would we analyze this to assess the pedestrian's outcome?

-F.

Again: although the image is not gorey, it may be disturbing to some. Please exercise discretion before clicking the link. http://poetry.rotten.com/redlight/
 
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I think the vehicle is a Mercedes Benz C-class wagon, with a curb weight ~3400 lbs.
 
To any of the crude (but clever) ways of estimating time lapse you suggested, I would affix a 'give or take a factor of 2'--meaning that if you estimate the car was moving 20 mph, I would say that the actual value was between 10 and 40mph--not very useful in determining whether the pedestrian could have survived.

I think the best way of obtaining time lapse would be to investigate further the meaning of the data printed across the top of the photo. Are any of the figures a time stamp? (If so, then why not include them along with hour and minute on the far left?)

The other thing you could do is google the date of the accident (June 26, 2002) and look for news items from Western Europe or possibly South Africa. (The date format, the spelling of 'Foto', and the lack of SUV's all say 'not North America'; the fact that everyone in the photo is white-skinned pretty much rules out most of Africa and Asia. Are those white bands on the fronts and backs of the cars license plates or the equivalent? The cars, manner of dress, and condition of the roads point to a fairly affluent society--much more likely to be in Germany or Switzerland than the Ukraine or Croatia.

P
 
It looks to me like the victim rotated a 3/4-turn. The legs were hit first, and in the second frame are pointing to the direction the vehicle came from. so the head and shoulders must have hit near the windshield base and probably jarred the wiper loose. There's no way the victim would have had time to grab anything.
 
came across this by googling; was posted on a local car forum and i wanted to see if there were any news reports.

to wit:

determining the average speed is trivial.

the merc has a known length, so one can determine distance traveled by the benz by measuring the pic by drawing lines and comparing length (in pixels) in powerpoint.

second, the time passed is 6.66 s - 5.85 s from the info in the pics.

from the spider-webbing of the windshield, the guy sustained a decent head injury, at a minimum.
 

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