I'm from Northern Ireland.
Gun crime in the UK is among the lowest in the world (rate of 0.7 per 100,000 in 2010, as opposed to 3 per 100,000 in the US).
The only country where police officers aren't banned from carrying guns in the UK is Northern Ireland.
UK statistics take into account gun related murders in Northern Ireland, and since, for the last I don't-know-how-many-years, there have been several shootings every year due to what we know as 'The troubles', and the effects of 'the troubles', a conflict between Paramiltary organisations, armed forces and police, and also 'punishment shootings', this causes the UK gun-crime rate to go up.
Also considering gun laws in Northern Ireland aren't as stringent as the rest of the UK, then the statistic always looks in the favour that gun-banning doesn't inherently work.
But if we take away the Northern Ireland statistics, the evidence is most definitely in favour of banning guns.