Va. Code § 46.2-882
The speed of any motor vehicle may be determined by the use of (i) a laser speed determination device, (ii) radar, (iii) a microcomputer device that is physically connected to an odometer cable and both measures and records distance traveled and elapsed time to determine the average speed of a motor vehicle, or (iv) a microcomputer device that is located aboard an airplane or helicopter and measures and records distance traveled and elapsed time to determine the average speed of a motor vehicle being operated on highways within the Interstate System of highways as defined in § 33.2-100. The speed of motor vehicles may be determined by the use of a photo speed monitoring device as authorized in § 46.2-882.1. The results of such determinations shall be accepted as prima facie evidence of the speed of such motor vehicle in any court or legal proceeding where the speed of the motor vehicle is at issue.
In any court or legal proceeding in which any question arises about the calibration or accuracy of any laser speed determination device, radar, microcomputer device, or photo speed monitoring device as described in this section used to determine the speed of any motor vehicle, a certificate, or a true copy thereof, showing the calibration or accuracy of (a) the speedometer of any vehicle, (b) any tuning fork employed in calibrating or testing the radar or other speed determination device, or (c) any other method employed in calibrating or testing any laser speed determination device or photo speed monitoring device, and when and by whom the calibration was made, shall be admissible as evidence of the facts therein stated. No calibration or testing of any device other than a photo speed monitoring device shall be valid for longer than six months. No calibration or testing of a photo speed monitoring device shall be valid for longer than 12 months.
The driver of any such motor vehicle may be arrested without a warrant under this section if the arresting officer is in uniform and displays his badge of authority and if the officer has observed the registration of the speed of such motor vehicle by the laser speed determination device, radar, or microcomputer device as described in this section, or has received a radio message from the officer who observed the speed of the motor vehicle registered by the laser speed determination device, radar, or microcomputer device as described in this section. However, in case of an arrest based on such a message, such radio message shall have been dispatched immediately after the speed of the motor vehicle was registered and furnished the license number or other positive identification of the vehicle and the registered speed to the arresting officer.
Neither State Police officers nor local law-enforcement officers shall use laser speed determination devices or radar, as described herein in airplanes or helicopters for the purpose of determining the speed of motor vehicles.
State Police officers may use laser speed determination devices, radar, and/or microcomputer devices as described in this section. All localities may use radar and laser speed determination devices to measure speed. State Police officers and local law-enforcement may use photo speed monitoring devices to measure speed as authorized in § 46.2-882.1. The Cities of Alexandria, Fairfax, Falls Church, Manassas, and Manassas Park and the Counties of Arlington, Fairfax, Loudoun, and Prince William and towns within such counties may use microcomputer devices as described in this section.
The Division of Purchases and Supply, pursuant to § 2.2-1112, shall determine the proper equipment used to determine the speed of motor vehicles and shall advise the respective law-enforcement officials of the same. Police chiefs and sheriffs shall ensure that all such equipment and devices purchased on or after July 1, 1986, meet or exceed the standards established by the Division.
Va. Code § 46.2-882