Right - well sorta.
The articles does state that more (detailed) data is needed . For example which laws were effective and which ones were not.
However the one true data that was used was a simple fact -> States that have more gun laws had fewer gun related deaths -vs- States that have liberal gun laws.
Sorta what Steve G said - just that single data point is enough said.
IMO; There should be a single source data base that all police departments report too, that is mandatory in every case . Some sort of an electronic file system or a check list .
Say a detective is call out to a new crime scene , he brings his department issued iPad
selects new case and a checklist pops up - type of crime and weapon of choice - there would be check boxes that once check goes auto into a national data base.
This would show how many criminal gun deaths -vs- gun deaths by accident -vs- gun deaths by self defense . Not to mention gun deaths -vs- knife deaths and so on.
I know its a dream - but this day and age it is certainly possible but I don't see anyone working to that direction ? ?