Ballistics experts can’t testify that recovered bullets match firearms, Md. high court rules

JohnKSa said:
The probability calculation would be difficult and would require a lot of groundwork, but might be possible. Things that would factor in:...
Click to expand...
Well, it might well be possible, but I do not think it would be at all practical. And given any realistic assessment of the error rates that have been seen, i do not think it would have any value.

In the in limine Daubert hearing, the circuit court instructed the state's expert to limit his testimony to whether a match was possible, not possible, or inconclusive. However, he testified, over objection, that there was a match. That led to the appeal and to the Supreme Court ruling
 
Last edited:
I wonder if more precise/CNC machining has made this area of study less conclusive? If the barrels/breach/face/firing pin, etc on a Glock (for instance) are more consistent/uniform now than things were 30 or so years ago maybe the "data" means a bit less now?
 
Ohen Cepel said:
I wonder if more precise/CNC machining has made this area of study less conclusive? If the barrels/breach/face/firing pin, etc on a Glock (for instance) are more consistent/uniform now than things were 30 or so years ago maybe the "data" means a bit less now?
Click to expand...
Doesn't matter. The issue is one of meeting the rules of evidence.
 
Kleanbore said:
Doesn't matter. The issue is one of meeting the rules of evidence.
Click to expand...

I am a scientist so am looking at it that way. I think it could matter as the deviations may be less with better manufacturing processes so therefore harder to detect. Sort of like detecting contamination in water, parts per 1000 was easy, million to billion got harder, but now need to do trillion for somethings. I don't know, but am simply speculating that the tolerances today may be similar enough between parts to make those calls tougher with any statistical power/certainty.

I cannot comment on the rules of evidence, not even sure what that means to be honest.
 
Bcwitt said:
What I was getting @ was if a handgun manufacturer buys barrel blanks (30" or so) cuts same blank to make pistols. All 6 pistols would have identical tool marks.
Click to expand...
Not necessarily, but that is not relevant to the topic.
 
In the early 2000's lead bullet analysis became an issue when FBI analyst Kathleen Lundy was using bad data to introduce as evidence in many trials that had to be retried because it was proven in the William Toobin studies that lead changes its composition enough from smelter to production so that it was not possible to say that a bullet or in this case lead shot came from a specific source. The FBI relied on this false data to convict many people. I have the complete analysis and case work on a CD. It's an enormous collection of data and it proves faulty techniques used by the feds to win cases in court. Lundy went to jail over this. There is a precedent for the federal government, aka FBI for using bad data to get convictions. My further contention is that 5 firearm barrels made from the same cutters, buttons etc., will leave marks so similar that they may be indistinguishable. Wear of the cutters would eventually change the markings but to what degree I don't have data for.
 
Bcwitt said:
What I was getting @ was if a handgun manufacturer buys barrel blanks (30" or so) cuts same blank to make pistols. All 6 pistols would have identical tool marks.
Click to expand...
As @Kleanbore noted, that's not really on topic, but I'll make one comment: I got to talk to the Firearms & Tool Marks people at our state crime lab a couple of years ago, and I had the same question. The answer was that they would not, because tool used to cut the blanks would have small amounts of wear as the process went along. IOW, if the manufacturer starts Blank #1 with a new tool, that tool will be slightly different by the time the manufacturer starts on Blank #2. That's probably oversimplified, but that's my understanding.
 
Last edited:
A cutting tool used @ a certain feed speed & proper coolant wont wear @ all. There is no way to be certain.
 
Bcwitt said:
What is your machinist credentials that you can say that? Do you have any metalworking experience?
Click to expand...
Some, but more importantly, my engineering education addressed mechanical design, materials science, manufacturing processes, physics, chemistry, and other relevant knowledge areas.
 
Cutting steel magnified and slowed down. - YouTube

You have to define what you mean by "wear" and "no wear". There isn't much wear evident for many of these video segments, but they aren't very long either. They are however HSS, which will wear faster and differently than the carbide tools used now.

While I find it possible to say that tool marks are reliable enough to use as evidence, I am very skeptical they can be used as sole evidence for a conviction. If the expert witness said the marks could only have been made by one gun, I wouldn't buy that.
 
Some OT posts have been removed. Let’s stay focused on the legal issues.

it appears that the bottom-line is that an expert can say that a particular bullet could have been fired from a particular gun, but not that it could only have been fired from that gun.
 
You must log in or register to reply here.

Similar threads

R
  • Locked
Fed Court accepts ballistic expert's matching of fired casings to a rifle
Replies
9
Views
1K
Firethorn
F
Spats McGee
  • Locked
  • Sticky
THE PECULIAR PROBLEM OF HANDLOADS IN SELF-DEFENSE SHOOTINGS:
Replies
0
Views
17K
Spats McGee
Spats McGee
D
  • Locked
(Eminent Domain follow up) High court asked to rehear Kelo case
Replies
23
Views
1K
Flyboy
F
J
  • Locked
Illinois Members, Appellate Court Rules a Glove Compartment may be a Case
Replies
10
Views
1K
illinisnare
I
C
  • Locked
New York "Appeals court affirms dismissal of state's lawsuit against gun makers"
Replies
8
Views
496
dinosaur
D
Back
Top