Holy questions batman
I will try my best to answer, although I have to go to sleep in 5 hrs 
tdrive2 wrote: OPP use Decatur genesis II i have seen it almost all cars. Along with the spectre 4/5 RDD's.
Moving: (these can all be used stationary, but are specific to which direction the car is in....to front or rear)
Decatur Genesis II, Genesis II Select, Genesis II Directional (K band)
Spectre 1, 2 and 3
Stalker DSR 2X Directional (Ka band)
Stationary: Handheld
Radar: Genesis VP, Genesis VP Directional (k band)
Lidar: Marksman LTI 20-20, Laser Atlanta Speed Laser
- I have not seen Ultralyte lidar for 6-7 years.
So the Decatur is a Kband always on radar.
yes k band, NO it is not always on
I noticed it has a front, rear, and patrol speed so the officer can get you without using a gun. So to clarify that means if you are racing up behind him in the left lane he can get your speed? And if you were racing away in front of him he could clock you to?
Yes
And this is Kband correct and not laser? Also is this radar "always on"???
k band is different than lidar, no not always on
The dectaur the officer sets a patrol speed. Lets say he puts 125 on and it will tell him if it picks up anything over that????
Can not set a patrol speed.
So my question is also are these vehicle specific? With a laser gun he looks in and points. But with a Decatur how can you be sure he got only your car????
- lidar is target specific, put the crosshairs on the vehicle, pull the trigger and that vehicle is that speed.
- radar transmits out a wider beam, but readings also correspond to the closest target, largest target and fastest target. Some radar units have settings to pickup vehicles greater than "x" speed faster than the patrol vehicle. Some units have a "faster mode". On 2 lane highways I use an elimination method to ensure I have the correct vehicle, even stationary on the 401 I use the method.
Are all hand held's laser?
No
Also another problem i see is how far is the Decatur actually reliable to? What if it was really far away in rainy weather and some guy cut in front of you going way faster he catches up and mistakes that guy with you?
The readings are still accurate, but the range is greatly affected and pending the moisture can go right down to nothing as the radar can not penetrate the moisture in the air and running down the windshield.
If the weather is rain, snow or fog, I will not be stopping much, I do not want to be on the shoulder for some dumb ass to rear end me.
Anyhoooo good cops do not get cold, wet or hungry......snow = cold,rain = wet, hungry = Tims 
I dont know if this is a rumor or not. I have heard an officer can give you a ticket without using a device to measure your speed???
yes....it would be disobey sign (maximum posted speed limit of "x"). I have never issued this offence based on observations alone for speed...having a speedometer and a vehicle passing me on the highway yes OR pacing a vehicle yes.
All lidar/radar actually does is give an actual number value for a speed.
Lets say you were going 55 over. How can he be sure it wasn't 49 over???
If you are speaking of an offence without a radar/lidar...I don't know, I wouldn't want to do that. Lidar and radar are both accurate and are all in favour of the defendant, due to cosine.
Above is merely a suggestion/thought and in no way constitutes legal advice or views of my employer. www.OHTA.ca