Question for any forensic ballistics guys (I know it is a long shot)

[spitfirejes]

If this is in the wrong sub-section I am sorry and feel free to move it to the correct one.

Back story:

Ok so I am currently getting blamed for damage to the front and rear windshield on a piece of machinery after a shooting meet. I lined two of my lasers thru the holes (ONE BLUE AND ONE GREEN) both hit the same location and the angle is not right from where my crew was shooting for it to be us. I also took my caliper micrometer and measured the inner diameter of the hole in the front windshield as there was a perfect circle with no elongation and the glass was fully intact. The holes diameter measured .493 inches.



My question:

Is there any way to tell what caliber would make a .493 inch diameter entry hole in glass.

And

Are there any other techniques I can use to provide further evidence?

Sent from a grassy knoll at 2,800 ft/s

 

[spitfirejes]

Micrometer lightly touching the entry hole.

Sent from a grassy knoll at 2,800 ft/s

 

[Maggot]

You are INNOCENT until PROVEN guilty. Accusations are not enough: The burden of proof lies with the accuser.

 

[kraigWY]

I cant tell you, no one can without examination of the scene. But having worked CSI and still being a Cert. LE CSI instructor I can give you an idea of the problems you will encounter.

Its rather difficult (unless you're on a TV show) to tell the bullet diameter by the bullet hole without a lot of tested which would require shooting the same distance, angle, velocity, etc. It also depends on the bullet.

Of course if you have two holes you can come close as to direction and angle, assuming the item shot wasn't moved.

But diameter is a different matter. A bullet going through an object creates two types of damage. First you have "contact damage" caused by the projectile itself. Then you have "induced damage" which is caused by the displaced target material. You can poke a hole with a WC bullet in paper that will cut without having induced damage. Then the same cal. bullet but with a round nose would cause the paper to tear, which pushed part of the paper target out, further tearing a hole in the paper.

Bullet construction also changes the sized of the hole also. A FMJ bullet will case induced damage as mentioned. A lead core, hollow point or lead exposed point, could have induced damage AND (depending on the velocity) will burn through the target material leaving a larger diameter hole. For example if you take a bullet and shoot it through a medium, it will leave one hole. If you invert the bullet where the lead bases is exposed, the lead can become extremely hot and melt its way through the target. You can see this by doing the experiment through mild steel. A bullet also works the same as a shape charge effect.

If shooting glass, the size of the induced damage will also be determined by the temper of the glass.

So in short there is no way to tell the diameter of the bullet via the bullet hole from the information provide. You "MIGHT" come close with careful examination. That would require hiring a forensic expert which would cost more the replacing the glass. But even that will not guarantee the results you're looking for. Too many variables.

I will tell you that having examined several bullet wounds and bullet damage over my years in LE CSI, is that two bullets fired from the same gun into the same target, don't give you the same results. You have to do some pretty extensive test.

 

[pawprint2]

There are three angles involved, the angle of the glass as it sets in the frame (up and down), the off set angle (left and right), both of these change based on the position of the car on the ground. For example if the car is sitting on a slope, or even if one tire is sitting in a depression, lastly you have the angle of impact, the actual angle of the bullet when it hit the glass. The real question is, why do people thing it was your round? The FBI has a standard, "windshield" test, the glass has a standard, the angle, the offset, and the distance fired, so 1000s of rounds have been fired and documented with those exact parameters, once they start changing, they become unique.

 

[Unknown]

They have the burden of proof, you don't. They have to prove it WAS you, all you have to do is provide reasonable doubt.

Besides, you can NEVER prove a negative. In other words, you can never prove something didn't, wouldn't, or couldn't happen, so you can't prove you didn't do it. They have to prove you DID.

Let them spend a metric ton of money hiring ballistic experts, then all you have to do is provide some reasonable doubt.

 

[spitfirejes]

Thank you guys for your answers

Sent from a grassy knoll at 2,800 ft/s

 

[40xs]

There is something to be said for; time of incident, opportunity, probability, reasonable assumption, any other similar activity than yours, greater weight of evidence, etc. etc...you get the picture, You were there, the damage was done, unfortunately---yada yada yada. It probably wont go this far but in civil suit damage awards "without a shadow of doubt" is not necessary, only the greater weight of evidence. "Wrong place,,Wrong time"!!