Day seven of the Delphi Murders Trial began with the testimony of Melissa Oberg. She is a former firearms examiner for the Indiana State Police. She was responsible for examining the single .40 caliber Smith & Wesson Winchester cartridge found at the crime scene near the Monon High Bridge Trail. The cartridge was found between the bodies of Abby Williams and Libby German. The girls' bodies were found in the woods near the bridge in Delphi on February 14, 2017. That unspent bullet or cartridge is significant evidence for the state's case against Richard Allen. The prosecution claims it ties Allen to the murder of the girls. Oberg testified for more than an hour Friday morning. She discussed how a firearm works and an explanation of the various parts that make up a cartridge. She explained to the jury how cartridge characteristics differ and why that is important. She also demonstrated to the jury how a semi-automatic pistol cycles cartridges from the time it is in the magazine, how it moves into the chamber, and then is ejected, either automatically if the round has been fired or manually by racking the action. Oberg talked about her initial observation of the cartridge found at the crime scene. She said she could see three ejector marks on the head, three extractor marks under the rim, miscellaneous marks on the primer, and various particles in the rim around the primer.Special Judge Fran Gull ordered a break from the proceedings at 10:30 a.m. Testimony is expected to continue Friday morning and is expected to continue into the afternoon. Oberg showed a diagram of firearm parts.She said an ejector pushes the cartridge out of the magazine and an extractor pulls the cartridge out. The two internal tools work together.Oberg showed the jury photos and videos of a cartridge in a chamber and cycling the cartridge. She identified her initials, and an ISP laboratory box labeled, Allens gun.She also demonstrated to the jury how a semi-automatic pistol cycles cartridges from the time it is in the magazine, how it moves into the chamber, and then is ejected, either automatically if the round has been fired or manually by racking the action.She showed three ways the cartridge could be ejected from the handgun.Oberg outlined her exam process as the following:Level 1 Analysis: Check the condition and class characteristics of the round, is it broken? Biometrics? Is there anything missing?Level 2 Analysis: Test fire with ammunition and use a comparison microscope to compare characteristics.Oberg testified she used a 60x magnification to observe markings on the "magic bullet." She said there are individual characteristics of a specific tools surface that can come from abuse, use or corrosion."Looking through the microscope is like watching a movie," Oberg said. "Pictures themselves don't represent everything we see in the examination process."Oberg compared a fired round from Allen's gun and the "magic bullet" found between the girls' bodies. She found the markings matched in three locations compared to the cycled round found at the crime scene.She said she could see three ejector marks on the head, three extractor marks under the rim, miscellaneous marks on the primer, and various particles in the rim around the primer.Oberg used articles of studies to reference her findings. Those studies, she said, were not the identical gun or exact extractor, but the conclusions of manufacturing process led the firearms examiner to feel confident in matching the cartridge to Allen's.Defense Attorney Brad Rozzi had objections because it wasn't the exact same model of the weapon.The court will see two videos of how SIG makes barrels and how pistols are put together after the lunch break.