here's what cops have mounted on their driver's side B-pillar up top just below the roof...about a foot long, half a foot wide cylinder...looks like a 3-pack of tennis balls...i would think it's radar but not 100%...and do u think it spreads a beam out, or is like a solid straight beam that u go past in order to activate a reading??? if it's a straight beam, it would suck for them if u spot them ahead

 

Can't be laser. Probably radar. I've seen them on the rear shelf before. Usually the strobe lights are atop.

 

External K or KA radar head. Usually facing backwards so they can park in the breakdown lane and monitor traffic coming up from behind.

 

Definitely RADAR.

Laser needs to be precisely aimed like a gun.
I believe some units even have scopes on so they can be REAL selective with the narrow beam.
They can pick off a single car in a pack of traffic.

Shawn S