Fact check: What methods do forensic ballistics use to match bullets to rifles?

1. Summary of the results

The methods used by forensic ballistics to match bullets to rifles involve comparing microscopic markings on shell casings and bullets, as well as using three-dimensional surface scans of breech face impressions on cartridge cases ^[1]. Congruent Matching Cells (CMC) is one such method that estimates the probability of random effects causing a false positive match ^[1]. Additionally, investigators can use the National Integrated Ballistic Information Network (NIBIN) database to compare digital images of shell casings ^{[2] [3]}. However, the reliability of these methods has been questioned, with some studies suggesting that inconclusive results can be predictive of innocence ^[4], and that subjective judgment based on training and experience is not sufficient to link shell casings to a suspect's gun ^[5]. New standards for forensic firearm examination, including the use of 3D technologies, have been proposed to increase the reliability and efficiency of forensic analysis ^[6].

2. Missing context/alternative viewpoints

A key aspect missing from the original statement is the limitation and potential flaws of current forensic ballistics methods ^{[4] [5]}. For instance, a study found that 85% of cartridge cases judged inconclusive by forensic firearm examiners were actually fired by two different guns ^[4]. Furthermore, the Oregon Court of Appeals has ruled that a forensic examiner's reliance on subjective judgment is not sufficient to link shell casings to a suspect's gun ^[5]. Alternative viewpoints also suggest that new technologies, such as 3D surface scanning microscopes, can improve the accuracy of forensic analysis ^{[7] [6]}. The use of expanded computer databases of ballistics images, like NIBIN, can also provide new tools for police investigating violent crime ^{[2] [3]}. It is essential to consider these alternative viewpoints to gain a comprehensive understanding of the methods used in forensic ballistics.

3. Potential misinformation/bias in the original statement

The original statement may be misleading, as it implies that forensic ballistics methods are more reliable than they actually are ^{[4] [5]}. The statement also fails to mention the potential biases and limitations of current methods, which can lead to false positives or inconclusive results ^{[4] [7]}. Additionally, the statement does not provide a balanced view of the different methods used in forensic ballistics, such as the use of NIBIN database ^{[2] [3]} or the proposed new standards for forensic firearm examination ^[6]. This lack of balance may benefit those who rely on the current methods, but it may not provide an accurate representation of the complexities and limitations of forensic ballistics ^[5]. Therefore, it is crucial to consider multiple sources and viewpoints to gain a comprehensive understanding of the topic ^{[1] [8] [2]}.