It has been more than 50 years since the assassination of President John F. Kennedy shocked the nation, but the case still generates considerable public interest—particularly fragments from the bullets that killed the president, which have been preserved in a temperature and humidity-controlled vault at the National Archives and Records Administration in Washington, DC, for decades. Scientists at the National Institute of Standards and Technology (NIST) recently teamed up with forensic experts at the National Archives to digitize the bullets, the better to preserve their features for the conspiracy theorists of tomorrow. All the data should be available in the National Archives’ online catalog sometime in early 2020.
There are two fragments of the bullets that killed JFK—one that hit him in the neck and another that hit him in the back of the head—as well as the so-called “stretcher bullet.” That’s the bullet that struck the president and also Texas Governor John Connally, found lying near the latter’s stretcher at the hospital. Also in the archives: two bullets used in a test firing of the assassin’s rifle for forensic matching purposes.
The curators from the National Archives were on site while all the analysis was being done, locking up the precious artifacts in a safe every night to ensure their safety. The biggest challenge, according to NIST’s Thomas Brian Renegar, was figuring out how to make measurements in sufficient detail to create the kind of 3D models they needed. For instance, “How do we hold the artifacts safely and securely?” he told Ars. “We don’t want them moving while we’re doing the scans, but we need to hold them carefully so as not to damage the artifacts.” The fragments in particular are also badly warped and twisted, making surface scanning difficult.
A typical ballistic analysis might focus primarily on the striations or markings to connect them to the firearm that produced them. The NIST team was much more thorough for their digital scans, measuring billions of points on the surface and generating some 360GB of data in the process. “Our task was to digitally preserve the entire object as best we could,” Renegar told Ars. “So we tried to scan the entire object as much as possible to preserve every nook and cranny on the bullets.”
There were two separate sets of measurements. First, the team used confocal microscopy to take high-resolution images of selected regions on the fragments. Next they used a focus-variation microscope to create a series of images from the surfaces of the bullet fragments at different focal distances. Finally, they used specially designed software to merge all the data together into one 3D model for each artifact. Renegar compared it to “solving a super-complicated 3D puzzle.”
The result: “The virtual artifacts are as close as possible to the real things,” said Martha Murphy, deputy director of government information services at the National Archives. “In some respects, they are better than the originals in that you can zoom in to see microscopic details.”
It’s part of ongoing work at NIST that introduced an open-access online database for ballistic tool marks in 2016. The organization is developing 3D surface mapping methods for future forensic analysis, employing a less subjective statistical approach, enabling forensic analysts to quantify how similar two bullets might be, rather than trying to make a visual match. The standard method is to view pairs of bullets side by side under a split-screen microscope to see if the striations line up.
Even though it was primarily done for historical preservation, and no forensic analysis was conducted, the process of digitizing the JFK assassination bullets tested and validated these new methods for ballistic analysis, on extremely distorted samples—by far the most difficult to analyze.
“A lot of the work [Renegar] did is important to the future because these are very difficult and singular types of samples,” NIST forensic firearms specialist Robert Thompson told Ars. “He was able to develop ways that will be helping forensic scientists and firearms examiners in the future, when this technology becomes more embedded in the crime laboratory. These are actual evidence specimens that are typical of what crime laboratories see all the time and have to analyze.”