"You will now read a transcript of testimony given by Terry Smith at trial."

"Q: Please state your name. <br/>
A: Terry Smith. <br/><br/>
Q: Who do you work for? <br/>
A: The local police department. <br/><br/>
Q: What do you do for the police department? <br/>
A: I am a firearms examiner. <br/><br/>
Q: How long have you been doing that? <br/>
A: 7 years. <br/><br/>
Q: What is a firearms examiner? <br/>
A: A firearms examiner is someone who looks at cartridge cases and bullets to determine whether 
they were fired from a particular firearm. <br/><br/>
Q: What training is required to become a firearms examiner with the local police department? <br/>
A: I received my bachelor's degree in forensic science and in 2015 I transferred to the crime lab 
from the crime scene unit. I underwent a two-year training program, which was supervised by experienced 
firearms examiners; I've toured manufacturing facilities and saw how firearms and ammunition were produced; 
and I've attended several national and regional meetings of firearms examiners."

"Q: And during the course of your career, were you tested in proficiency to make sure you were still conducting
appropriate examinations? <br/>
A: Yes. I have undergone annual proficiency examinations. <br/><br/>
Q: Is the local police department lab accredited? <br/>
A: Yes, it is accredited by ASCLID/LAB. <br/><br/>
Q: And in addition to what you just told us, do you have other qualifications? <br/>
A: Yes, I do. <br/><br/>
Q: Can you tell us what those are? <br/>
A: Yes. I received training in the use of a bullet matching algorithm. This is an algorithm that evaluates
the characteristics of two fired bullets, in order to produce a score for the similarity of the bullets, where
more similar bullets are more likely to have been fired from the same gun. I attended a workshop on the algorithm
on 1/11/2020, held by CSAFE - Center for Statistics and Applications in Forensic Evidence. The training taught me to use the
algorithm alongside my personal judgement. I found that my conclusion was reflected in the similarity score produced 
by the algorithm in all 21 cases."

"Q: Where does the bullet matching algorithm come from? <br/>
A: It was created by Dr. Adrian Jones. <br/><br/>
Q: How long have the state police been using the bullet matching algorithm? <br/>
A: They have been using it since January of 2020. <br/><br/>
Q: Have you testified in court previously using the bullet matching algorithm? <br/>
A: Yes, I have, approximately 10 times. <br/><br/>
Q: As a firearms examiner, have you testified about your conclusions, given the results of your testing? <br/>
A: Yes, I have. <br/><br/>
Prosecution: Your Honor, at this time I would ask that Terry Smith be qualified as an expert in the field of 
firearms identification subject to cross examination. <br/>
Court: Any cross on their credentials? <br/>
Defense: No, Your Honor. <br/>
Court: This witness is an expert in the area of firearms identification. They can testify to their opinions as 
well as facts. Go ahead."

"Q: What work did you do on this case? <br/>
A: I was asked to compare a bullet from the crime scene to a test fire from the gun recovered from the traffic stop. <br/><br/>
Q: Did you examine how many lands and grooves the bullet had? <br/>
A: Yes. <br/><br/>
Q: Can you explain for the jury what that means? <br/>
A: Yes. In the interior of a barrel there are raised portions called lands and depressed areas called grooves. 
When a bullet passes down the barrel, a bullet will spin and that gives it stability and accuracy over a distance. 
Those raised areas are designed by the manufacturer. They're cut into the barrel. And each particular file has a 
different combination of lands and grooves. But essentially what those lands do is grip a bullet and spin it, and 
as that bullet passes down the barrel, it scratches the random imperfections of that barrel into the bullet."

"Q: Now, for these bullets, you counted up the lands and grooves and determined the direction of the twist, correct? <br/>
A: Yes. This bullet had six lands. And the interior of the barrel, the barrel will either twist right or it will twist left. 
And in this particular case, the barrel twists right. And you can see that by looking at the bullet. If you look at the base 
of the bullet, either it goes to the left or goes to the right. 
Exhibit A depicts a cross-section of a barrel, where rifling is clearly present. Exhibit B depicts an example of a 
fired bullet, with which includes lands and grooves.<br/>
<center>---Exhibit A---</center><br/>
<img src=\"rifling.jpg\" alt=\"rifling\" style=\"width: 50%\" height=\"\" class=\"center\"><br/><br/>
<center>---Exhibit B---</center><br/>
<img src=\"fired_bullet.jpg\" alt=\"fired_bullet\" style=\"width: 50%\" height=\"\" class=\"center\"><br/>
<br/><br/><center>---Test-fired bullets admitted into evidence---</center><br/><br/>
Q: Can you describe the process of obtaining these test-fired bullets? <br/>
A: The test-fired bullets came from a test fire of the gun recovered from the traffic stop. <br/><br/>
Q: You mentioned test firings; can you explain what that means? <br/>
A: In test firing, first what I would do is make sure the firearm is safe to actually test fire. Then
I would use lab ammunition and I would test fire it, meaning that I am creating a fired bullet. Typically
you do two at a time. That way you have a fired bullet to compare to another fired bullet. <br/><br/>
Q: Would you then have taken the test firings you created and did you compare those test firings to the
fired evidence that you had also received?<br/>
A: Yes. First what I would do is compare my test shot to test shot. I am looking for a detailed
microscopic pattern. Once I have done that then I would compare it to the fired evidence. <br/><br/>

Q: And how about the number of lands and direction of twist for the test fires? <br/>
A: It also had six lands, and twisted to the right. <br/><br/>
Q: Okay. Now, did you compare the test-fired bullets to the fired evidence under the comparison microscope? <br/>
A: Yes, I did. <br/><br/>
Q: What is your conclusion? <br/>
A: I found that there was significant disagreement in individual characteristics."

"Q: How were you able to conclude that? <br/>
A: I place them under the comparison microscope, and I roll the bullet around until I can see the agreement in a particular 
area: unique surface contour that has sufficient agreement. At that point, when I've seen that, I start to rotate the bullets 
around and I look at all the different lands and grooves, impressions, for that unique detail. When I can see those, that agreement 
on multiple areas of the bullet, I identify the bullet as having sufficient agreement. When I see disagreement in multiple areas
of the bullet, I identify the bullet as having significant disagreement. 
Exhibit C shows an image of a comparison microscope, as well an an example of a matching bullet comparison. <br/>
<center>---Exhibit C---</center><br/>
<img src=\"microscope.jpg\" alt=\"microscope\" style=\"width: 50%\" height=\"\" class=\"center\"><br/>
Q: Did you use an algorithm to compare these bullets as well? <br/>
A: Yes, I used the algorithm to compare the two test fires to each other. I also used the algorithm
to compare the better-marking test fire to the fired evidence that I received.<br/><br/>
Q: Could you explain how this algorithm compares bullets? <br/>
A: The algorithm uses 3D measurements to make a comparison between the surface contours of each of the lands on each bullet.
These comparisons result in a match score between 0 and 1, where 1 indicates a clear match, and 0 indicates that there is 
not a match. The bullet is aligned based on the maximum agreement between the lands, and the average match score for the lands
is computed. This average score gives an overall match score for the entire bullet.<br/><br/>
Q: What was the match score between the two test-fired bullets?<br/>
A: The match score was 0.976. 
Exhibit D shows the comparison grid between the two test-fired bullets.<br/>
<center>---Exhibit D---</center><br/>
<img src=\"Test_Fire_F526.jpg\" alt=\"test_fire\" style=\"width: 50%\" height=\"\" class=\"center\"><br/>

Q: What was the match score between the better-marked test fire bullet and the fired evidence? <br/>
A: The match score was 0.034. <br/><br/>
Q: What does this match score indicate about the bullets? <br/>
A: The match score indicates that there is significant disagreement between the two bullets. 
Exhibit E shows the comparison grid between the test-fired bullet and the fired evidence.<br/>
<center>---Exhibit E---</center><br/>
<img src=\"K995_NoMatch_SingleGrid.jpg\" alt=\"tree_grid\" style=\"width: 50%\" height=\"\" class=\"center\">"

"Q: Now, how many times have you compared bullets to determine if they were fired from the same gun? <br/>
A: I'd say thousands. <br/><br/>
Q: And do you ever see two bullets that have agreement in every single area of the bullet? <br/>
A: No. When firing a firearm there is a dynamic process because it is a contained explosion. When the firing pin hits the primer, which is 
basically the initiator, what gets it going, it will explode, burn the gun powder inside the casing, and the bullet will travel down
the barrel, picking up the microscopic imperfections of the barrel, and the cartridge case will slam rearward against the support 
mechanism. During that dynamic process, each time it happens, a bullet will be marked slightly differently from one to the next. <br/><br/>
Q: When you reached a conclusion, did you write up a report? <br/>
A: Yes, I did. <br/><br/>
Q: Is it the local police department's protocol to have somebody else who's a firearms tool mark examiner in your lab review that report, 
review your work, and determine if it's correct? <br/>
A: Yes. <br/><br/>
Q: That's what we call peer review? <br/>
A: Peer review, yes. <br/><br/>
Q: Thank you, no further questions."

"<center>---Cross Examination---</center><br/>
Q: Now, are you telling the jury today that when one firearm fires two bullets, the individual markings are so similar that you can
say that they were fired from a single gun? <br/>
A: Yes, when there is significant similarity, the probability that the two markings were made by different sources is so small that it
is negligible. <br/><br/>
Q: So that is not what you observed in this case? <br/>
A: In this case, the accidental, random marks on the bullets from the firing process were substantially different - enough so to conclude
that the two bullets were likely fired from different guns. <br/><br/>
Q: That's your opinion. And your opinion, by the way, is subjective, right? And it's based on your experience? <br/>
A: Based on my training and experience, yes. <br/><br/>
Q: Is there something fixed about the amount of what has to be found to constitute sufficient agreement? <br/>
A: No, there is not a fixed amount or a numerical value for my visual comparison. For the algorithm, however,
a score below 0.3 is a general indicator of sufficient disagreement."

"Q: How long did you say you've been trained in the bullet matching algorithm? <br/>
A: Since January of 2020. <br/><br/>
Q: Okay. So that's fairly new, is that fair to say? <br/>
A: It is still fairly new, yes. <br/><br/>
Q: The software uses modeling; is that correct? <br/>
A: Yes, it does. <br/><br/>
Q: You, personally, don't know the source code; is that correct? <br/>
A: That's correct. <br/><br/>
Q: And, in fact, you, personally, would not be able to tell us the specific math that goes into this program; is that fair to say? <br/>
A: We did receive training on what the math is doing in general terms, but I am not a statistician, 
and would prefer to let them speak to that.<br/><br/>

<center>---Questions Submitted By the Jury---</center><br/>
The Court: Terry Smith, the jury has asked me to forward this question to you. Answer if you're able.
To what percentage is the science accurate is the first question. And then I think the rest of that explanation of that 
question goes on to say, to determine that the bullets were fired from a different firearm, are you 100 percent sure? <br/>
A: My opinion, I am 100 percent sure that these bullets were fired from different firearms. There is a published error
rate for firearms examiners. The false negative identification rate is less than three percent. I believe it's about 1.5 to 1.9.
That's just a general number that's out there."
