Understanding the Use of Radar in Court Proceedings: Timing and Accuracy

In the realm of law enforcement and traffic control, radar and lidar guns play a crucial role in measuring vehicle speed with precision. These devices are often subject to scrutiny in court, and one common question that arises is about the 'radar hold'—the time frame during which a radar must detect a vehicle before it can be trusted in a legal proceeding. This article dissects the process and explains when and how a police officer uses radar to measure speed and provide a valid reading in court.

Radar and Lidar Basics

Radar and lidar guns are sophisticated pieces of technology designed to accurately measure the speed of vehicles. Radar uses radio waves to measure the speed, while lidar employs laser technology to achieve the same goal. These devices do not provide a reading immediately; instead, they require a series of signals to ensure accuracy.

Radar Technology and Timing

Radar devices typically require several cycles of signal transmission and reception to obtain a reliable speed measurement. This ensures that the reading is not a false positive due to atmospheric interference or other external factors. The process is nearly instantaneous, as the radio waves travel at the speed of light, but the device must confirm multiple readings to ensure reliability.

Lidar Technology and Timing

Lidar devices, on the other hand, take slightly longer to provide a measurement. Typical lidar devices require about 1 to 1.5 seconds to obtain a speed measurement. This extended time frame is necessary to ensure that the laser pulse interacts with the vehicle and returns a valid signal. The extended duration is especially important in legal settings to provide a comprehensive and reliable reading.

Police Officer Testimonies and Legal Reliability

A police officer does not need to 'hold' the radar for a specific duration to provide a valid reading in court. The officer's primary responsibility is to ensure that the radar unit is functioning properly and that the reading is accurate. As long as the officer can testify that the device is in good working order and that the reading was obtained through proper usage, the reading can be considered reliable.

Holding the Beam for Verification

Officers often track a car for a few seconds to confirm that they have the correct vehicle before holding steady. This is a standard practice to ensure that the radar is detecting the intended vehicle. If the driver applies the brakes suddenly, this can also provide a clear signal to the officer that the radar is functioning correctly. The sudden deceleration confirms that the radar is picking up a valid signal.

Modern Detector Interactions

For officers who regularly face the challenge of speeders using radar and lidar detectors, the process can be more complex. Detectors often use additional signals to detect the presence of law enforcement devices. Skilled officers like those mentioned in the example have developed strategies to overcome these challenges. When a detector is activated, officers may turn the radar beam on and off to lock in on the external monitor, which helps in confirming the correct vehicle. They also listen for audible signals from the dash unit, the pitch of which indicates the speed of the vehicle.

A Case Study

The author of this article recounts a vivid experience of using radar and lidar guns in their law enforcement career. They mention catching a driver going over 135MPH, who then attempted to evade the officers by changing routes. The officer called ahead and another unit was waiting to catch the speeding vehicle. The case was a testament to the reliability and accuracy of radar technology in real-world scenarios.

While the 'radar hold' is often a point of confusion, the process of using these devices is well-defined. As long as the officer can demonstrate that the device is in proper working order and that the reading was accurate, the reading can be trusted in court. Modern technology has made speed measurement more reliable, and skilled officers continue to refine their techniques to combat the use of speed detectors.