In order for a criminal use to be notable enough for inclusion in the article on the gun used, it must meet some criteria. For instance, legislation being passed as a result of the gun's usage (ex. ban on mail-order of firearms after use of the Carcano in JFK's assassination would qualify). Similarly, if its notoriety greatly increased (ex. the Intratec TEC-DC9 became infamous as a direct result of Columbine). As per WP:UNDUE, "Neutrality requires that each article or other page in the mainspace fairly represent all significant viewpoints that have been published by reliable sources, in proportion to the prominence of each viewpoint in the published, reliable sources.".
In order for a criminal use to be notable enough for inclusion in the article on the gun used, it should meet some criteria. Examples of notability criteria include, but are not limited to, legislation being passed as a result of the gun's usage (ex. ban on mail-order of firearms after use of the Carcano in JFK's assassination would qualify) or an increase in notoriety (ex. the Intratec TEC-DC9 became infamous as a direct result of Columbine). As per WP:UNDUE, "Neutrality requires that each article or other page in the mainspace fairly represent all significant viewpoints that have been published by reliable sources, in proportion to the prominence of each viewpoint in the published, reliable sources.". The issue of when criminal use is relevant and when it is not is a talk page issue.