Next witness: Steven Aston, forensic scientist, specializes in firearm ballistic research and testing. Discussing bullet vs. cartridge comparisons. Studies the tool marks on the projectile and the tool marks on the cartridge to determine firearm source.
After about 30-45 minutes+ of Aston going through his credentials, Aston declares that he is a certified expert of firearms examinations. He claims he has never made a mistake in his work. We are now about to discuss Aston's work on the Armstrong case.
Aston discussing the testing of firearms. A weapon needing analysis is fired four times, the cartridge cases are recovered and so are the projectiles. These are called "knowns." They are then compared to the evidence found at the crime scene ("unknowns”).
There is a lot of firearm technical terms and jargon being thrown around. The prosecution is attempting to build credibility and foundation, but it is a tedious and technical testimony. Can't help but wonder if the jury is zoning out. You can definitely tell the gallery is.
Aston discussing the unique grooves and cuts inside the barrel of a gun, giving each bullet a distinct marking and adding stability to spiraling projectile.
Aston says he looks through a microscope upwards of 60x magnification to compare tool marks on knowns and unknowns side-by-side.
Aston discussing "individual characteristics" that a weapon has. Must look at the totality of their evidence and the level of agreement shown in test firings. Some jury members look bored. Mo's brother rests his head on a friend's shoulder and takes a nap. Can't blame him.
I remember during opening statements that the defense plans on pushing that ballistic science is not an exact science and can be easily misinterpreted. It's likely the reason why the prosecution is diving so deep into how Aston knows what he knows and what exactly ballistic examinations entail.
Here we go. Prosecution now asking about Aston's experience studying the Armstrong case. Aston was asked to perform two different sets of analysis.1) Provided three fired cartridge cases, two firearms, a magazine, a loader and a pistol case
Two guns examined: Sig Sauer 9mm pistol and a Springfield Armory EMP Roman 9mm pistol.
Aston being asked to examine spent 9mm cartridges cases that are inside a large, transparent ziploc evidence bags. Aston puts on black surgical gloves and removes one of the cartridges for the jury to see. You can see the unique identifier and Aston's initials.
Aston places the spent shell casing on a projector that displays it to the entire courtroom & jury. You can see the head stamp, the lettering "JAG" (manufacturer). You can see the silver primer and an hemispherical indentation from the firing pin.
The cartridge is then placed on its side on the projector. You can now see the profile of the case. The primer is on the left. Inside of it would have been the gunpowder and the projectile. Because this cartridge has already been fired, there is no bullet.
We are now looking at additional lab items. One item has moderate impact damage, another has heavy impact damage, the third is "five copper lead projectile fragments.”
More evidence being admitted: photographs of projectiles. They are being displayed to the jury. They are large yellow envelopes. They have Austin Police Department red tape on them. Orange labels show "Hazard: Handle with Gloves." You can see the case number and the word MURDER.
In a different photo, you can see the projectiles now placed on top of the manila envelopes. The first bullet has a red stain on it. The second bullet has hair attached to it. The third has reddish brown stains on it. Inside the final envelope are five copper/lead fragments.
Mo Wilson's mother has her head lowered toward her lap. Mo Wilson's father rubs her shoulders and neck. Mo Wilson's brother has stepped out of the courtroom. Kaitlin Armstrong is sitting still. She is blinking, but it is not clear what she is looking at. The jury is listening closely to Aston speak.
The bullets are heavily melted and disfigured. The first bullet is nearly flat. The fragments range in size.
Aston says he compared the casings found at the crime scene to those at the test firing lab. We are now looking at a side-by-side comparison.
The first photo shows a side-by-side comparison of two cartridges found at the crime scene. Aston says he was looking for agreement. The two cartridges show "significant agreement," Aston says.
Slight disagreements are expected because of the pressure it takes to fire a bullet from a gun, Aston says. It may cause the images to not line up perfectly. But he says he is looking for majority agreement.
Now it's time to compare the cartridges found at the crime scene to the cartridges from the test firing. Aston: "Just like we saw when we compared those from the scene, we are seeing the same amount of agreement from the bottom all the way to the top.""When you look at the gouges, this line, that line... we are still seeing the same amount of agreement that we saw on the evidence" from the crime scene.
If you are trying to picture this in your head, think of pictures of highly magnified copper magazines. You can see every single groove, line and detail. On the left is the crime scene magazine, on the right is the test firing.- The two photos are lined up perfectly so that one photo seemingly blends into the other. This is what Aston means when he says "agreement.”
Aston says he was able to reach a conclusion: That the crime scene projectiles were fired from the Sig Sauer 9mm. Following the test firings, he was able to definitively eliminate the Springfield 9mm from contention as the weapon used in the killing of Mo Wilson.
Witness passed.
-- Defense's turn
Defense asks if Aston is an expert of JAG and ammunition. Also asks if his line of work should be considered as subjective opinion. Aston agrees, yes, the findings are his opinion.
Context: JAG was printed on the shell casings. JAG was bought out by Ammo Inc in 2019. But JAG is not the only headstamp found on Ammo Inc. ammunition and JAG headstamps are pretty common, in general.
Defense is reading an article from the Association of Firearms and Tool Mark Examiners which posited that agreement lines found in test firings might closely resemble two different guns. A good strategy to add doubt in the minds of the jurors of the credibility of the testimony.
Defense is really hounding the witness on his credibility and his profession. Aston says he has never failed a proficiency test for ballistics testing or made a mistake on a proficiency test.
Aston clarifying tool mark examinations versus firearms examinations. Aston is a tool mark examiner, meaning he can also study markings from screwdrivers, hammers and other tools. Aston says he doesn't deal with numbers or data, so his work is subjective by nature.
Aston says there is no "quantity of agreement" for him to call evidence he is eyeballing a match. No minimum points of agreement to meet a threshold. Therefore, the agreement levels can differ examiner-to-examiner.
Court has adjourned for the evening. Thanks for following along. See you back here bright and early tomorrow.
Have a wonderful night.
