A seemingly insignificant piece of a bathroom door lock, described as a metal ring roughly the size of a quarter, proved to be the key piece of evidence that led to Matthew Ecker being charged with the murder of Alexandra Pennig. Details regarding how the ring connected Ecker to the crime scene haven't been fully released, but its discovery was instrumental in building the case against him. The investigation highlights the importance of meticulous forensic work and how even the smallest fragments can provide crucial links in solving complex criminal cases.