I suppose in your post you actually meant affect police lidar (laser) and not radar.
Yes. Reflected sunlight does affect police lidar, but not in the way you are hoping, I am afraid.
What is the most likely outcome is that in these particular circumstances the effective range of police lidar is reduced
. Police lasers employ something called AGC (automatic gain control) which automatically adjusts the police laser guns on sensitivity.
If you think of a police laser gun as a camera with automatic exposure compensation settings, you'll get the idea. When you take a picture of someone while facing direct sunlight, your camera will adjust its exposure to properly expose the backgound, but all too often the individual is underexposed. The same kind of phenomenon happens with police laser.
I have targeted highly reflective vehicles while the sun was behind me and low in the sky and have found the in certain circumstances the range of police laser can be reduced by as much as 50% just by the angles. When the angles change sufficiently enough where the reflection goes away, the range increases again.
Police laser also use pretty sophisticated algorithms to accurately calculate your speed and if something like excessive direct or reflected sunlight adversely affected the lidar gun, error codes could also be the result, but not invalid speed readings.
I believe that, in general, these kinds of lighting conditions, will tend to always favor the driver
and not the lidar operator.