{"id":355884,"date":"2016-04-04T11:04:32","date_gmt":"2016-04-04T16:04:32","guid":{"rendered":"https:\/\/content.findlaw-admin.com\/ability-law\/traffic\/traffic-stops\/can-i-challenge-radar-gun-evidence-in-court.html"},"modified":"2023-11-25T13:43:41","modified_gmt":"2023-11-25T18:43:41","slug":"can-i-challenge-radar-gun-evidence-in-court","status":"publish","type":"page","link":"https:\/\/www.findlaw.com\/traffic\/traffic-stops\/can-i-challenge-radar-gun-evidence-in-court.html","title":{"rendered":"Challenging Police Radar Gun Evidence in Traffic Court"},"content":{"rendered":"\n
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Challenging Police Radar Gun Evidence in Traffic Court<\/h1>\n
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\n By Natalie Moritz<\/a> | Legally reviewed by Melissa Bender, Esq.<\/a>\n | Last reviewed\n
\n \n <\/i>\n Legally Reviewed\n <\/summary>\n\n
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This article has been written and reviewed for legal accuracy, clarity, and style by FindLaw\u2019s team of legal writers and attorneys<\/a> and in accordance with our editorial standards<\/a>.<\/em><\/p>\n\n <\/div>\n <\/details>\n\n

\n \n <\/i>\n Fact-Checked\n <\/summary>\n\n
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The last updated date refers to the last time this article was reviewed by FindLaw or one of our contributing authors<\/a>. We make every effort to keep our articles updated. For information regarding a specific legal issue affecting you, please contact an attorney in your area<\/a>.<\/em><\/p>\n\n <\/div>\n <\/details>\n<\/section>\n

Radar guns are valuable tools for detecting a vehicle’s speed, but like all measurement devices, they are not perfect technology. In addition, they are operated by law enforcement officers and are not immune to human error.<\/p>\r\n

If the police have cited<\/a> you for speeding based on a radar gun reading, you can challenge the evidence in court<\/a> based on the limitations of radar guns. Read on to learn more.<\/p>\r\n

How Radar Guns Work<\/h2>\r\n

Radar guns are devices that both send and receive radio signals. They work by directing a radio signal towards a vehicle and then receiving the same signal as it bounces off the vehicle. Using the Doppler Effect<\/a>, the device can calculate the speed of the vehicle based on changes in the value of the returning signal.<\/p>\r\n

Many law enforcement agencies have adopted Light Detection and Ranging (LIDAR)<\/a> technology. LIDAR operates similarly to radar but uses lasers instead of radio waves.<\/p>\r\n

Before challenging a speeding ticket in traffic court<\/a>, you need to know what speed detection device the officer used. Besides radar guns and LIDAR, some agencies may also use pacing or VASCAR to measure speed. VASCAR (Visual Average Speed Computer and Recorder) is a recent technology that determines speed by calculating the time a motorist takes to travel between two points.<\/p>\r\n

Regardless of which technology the agency uses, these devices are sensitive tools of measurement that require regular calibration and adjustment. Radar guns, for example, require the use of a tuning fork to ensure the device is producing accurate readings. Device manufacturers devices recommend calibration before every use. However, some states may require testing and calibration less frequently.<\/p>\r\n

Radar Gun Fast Facts<\/h2>\r\n

Radar guns use three types of frequency bands to transmit the radio waves used to detect speed:<\/p>\r\n