A court hearing involving the deaths of two Australian brothers and their American friend in Mexico has heard new evidence about the firearm recovered during the investigation.

A firearms expert told the court that a gun entered into evidence was not the weapon used to kill the three men. The evidence adds another development to a case that has attracted significant attention because of the deaths of Australian nationals overseas.

The hearing is examining forensic evidence surrounding the killings and the circumstances in which the victims died. Investigators have been working to establish what weapons were used and how the evidence recovered during the investigation relates to the deaths.

According to the latest court evidence reported by ABC News, the firearm presented as an exhibit was examined by an expert. The expert concluded that it did not match the weapon responsible for the fatal shootings. This distinction is significant because firearms examination can help investigators determine whether a particular weapon was used in a crime by comparing characteristics such as ammunition, markings and other forensic evidence.

The case concerns two Australian brothers and their American friend who were killed in Mexico. Their deaths have led to an ongoing investigation and legal proceedings examining the evidence surrounding the incident.

The court's consideration of the firearm evidence forms part of the broader process of determining what happened and who was responsible. Evidence presented during criminal proceedings can include forensic examinations, witness testimony and material recovered by investigators.

The firearms expert's evidence does not by itself establish what weapon was used in the killings. Instead, it addresses the particular firearm that had been entered into evidence and its relationship to the shootings. Further evidence and testimony will be considered by the court as proceedings continue.

Cases involving killings overseas can involve investigations across different jurisdictions, with evidence collected at crime scenes potentially examined by specialists at different stages. Establishing the provenance and relevance of physical evidence can therefore become an important part of court proceedings.

The latest hearing provides another insight into the forensic investigation surrounding the deaths. The distinction between a weapon recovered or presented during an investigation and the actual murder weapon may become relevant as prosecutors and defence lawyers examine the evidence before the court.

Further proceedings are expected to consider additional evidence connected with the deaths and the circumstances surrounding the case.

The court will continue assessing the evidence presented during the proceedings. Any findings about responsibility will depend on the evidence considered by the court rather than on the identification of a particular firearm alone.