Bullet Trajectories

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ddustin
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Bullet Trajectories

Post by ddustin »

Eugene Liscio, my son Jesse and I attended a Shooting Incident Reconstruction class this last week in Omaha, NE.
Here is an image from a scan we took and how we created trajectories from the scan.
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Re: Bullet Trajectories

Post by jcoco3 »

Very cool, You guys have all the fun! Who had the pleasure of gunning down the old clunker?
It looks like some bullets hit the front glass. Is it possible to establish a bullet trajectory when the bullet goes through safety glass?
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Re: Bullet Trajectories

Post by ddustin »

A former FBI Agent did the perforation.
As far as determining trajectory through glass, it is certainly possible but you need a reliable point of termination (essentially 2 points).
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Re: Bullet Trajectories

Post by jcoco3 »

:lol: "perforation"

Two points makes sense. Learn something everyday.
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Re: Bullet Trajectories

Post by ddustin »

jcoco3 wrote::lol: "perforation"

Two points makes sense. Learn something everyday.
Actually, I wasn't trying to be funny (for a change). Perforation is correct when describing the nature of the hole.

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Re: Bullet Trajectories

Post by jcoco3 »

I learned two things today :D Its been a good day!
...I still think that word is an amusing way to describe a bullet hole, but in all seriousness I really need to attend one of your presentations. I know so little about the forensics industry :( I assume you or Eugene will be presenting at the Faro conference?

Not trying to detract from the topic here, so I have a couple more questions to get back on track. I have noticed from other post here that wood dowels with spherical targets on the same axis passing through the "perforations" seem to be a good way to establish trajectory, but I assume that they require either two points of perforation or 1 long cylindrical perforation to establish a good trajectory. Is there anyway to establish trajectory from a single impact location like a concrete wall or steel plate that the bullet did not penetrate completely? Sorry if this is something previously covered, but it seems like it might be possible after scanning the impact site in high resolution and comparing the scans to some test scans where the origin of the bullet was known.
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Re: Bullet Trajectories

Post by 3DForensics »

Depending on the material you can often make an estimate of the direction from which the bullet impacted a location based on the shape of the hole. A circular impact is at 90° to the surface and as it becomes more oblique, the hole turns to an ellipse. You can use the equation:

sin (Θ) = width/length

theta is the angle of impact
width is the minor axis of the ellipse
length is the major axis of the ellipse

This is an estimate though and usually, the more elliptical the shape, the more accurate the result. Angles close to 90° are difficult to estimate since they are very close to circular and a small change in the width to length ratio has a big change in the impact angle.

This is the same premise as bloodstain pattern analysis. This is video that I made some time ago showing the projection of a blood drop on a tiled floor. It is the same for a stable bullet in flight.


youtu.be/M1TzSkrS2YM

https://www.youtube.com/watch?v=M1TzSkrS2YM

Cheers,

Eugene
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