Gatso flash how does gatso work?

It sends out a radar beam which bounces back from a passing vehicle measured over a set time and distance. If the radar is placed wrongly, for instance on a bend in the road, or used from inside a vehicle it may give incorrect results.

The Home Office has approved the Gatso Type 24 for use in both fixed and mobile uses each of which has a Schedule of Conditions to its Type Approval which must be met in order for the information from the device to be able to be used as evidence of an offence.
The above Type Approval is for the UK speed enforcement only. Other countries may have similar approval requirements

Also for the UK, once a device has recorded an alleged speeding offence the Registered Keeper (RK) must receive a Notice of Intended Prosecution (NIP) asking for details of the driver of the vehicle at that time and place.
Any late service of this NIP still requires the RK still has to complete the information but any penalty for speeding is invalidated due to late service of the NIP.

Once the police are informed of the driver details they can then either issue a Conditional Offer of Fixed Penalty, usually 3 points on the drivers license plus a fine of £60, or if the police consider the speed was excessively above the limit they can issue a summons to appear in court. In cases where the speed was only slightly over the limit they may also offer the driver the option of attending a Speed Awareness Course. This entails a day on a course at some sort of cost (usually around £90) but doesn't result in any points being put onto the drivers licence.

Any speeding summons must be laid before the court before the expiry of 6 months from the date of the offence otherwise they cannot prosecute due to time-out.

Return of the NIP has to be made within 28 days of service giving the details required. Failure to do this will result in the RK being prosecuted for the offence of not giving the driver details. The only defence against this summons is that the RK has used Due Diligence in trying to find out who the driver was and can prove this to the satisfaction of the court. It must be borne in mind that a simple, "I don't know who was driving will not suffice".

Any summons for failing to identify the driver is required to be laid before the court before the expiry of 6 months from the expiry of the 28 days given to identify the driver, ie usually within 7 months of the date of the alleged speeding offence. Failure to lay information for the offence before the end of this time renders the police incapable of prosecutiong for the offence.