The author is a high-end computer programmer (in charge of Java language over at Google) and got a speeding ticket with a wildly different reading than his car was indicating. So he did some research for his defense.

He covers how LIDAR can have a bad reading:

https://docs.google.com/file/d/0B941.../view?sle=true

Short summary:

- NHTSA says readings are only valid when used from a tripod (otherwise hand shake affects readings)
- Speeds over 70mph were not tested
- Range was 1000ft max
- Beam spread can be .3 degrees or more. Exacerbated by reading at an angle. At 1000 ft, .3 spread covers multiple traffic lanes.