The problem here isn’t how accurate a LEO could be in estimating speed, but the potential for abuse in allowing officers to “make their case” solely on such grounds.
The problem here is potential for abuse. I’m not as worried about the 25% that can’t WAG a car’s speed as I am the 5% that would abuse the discretion to do so.
Gov’t - and its agents - must be kept in check. That is the essence of “limited government”.
That's certainly possible, but it would also catch up to the officer and eventually wreck his career. After you get smacked hard in court a few times with evidence that shows you're way off, your professional opinions and estimates soon don't mean much any more. When that happens, your usefulness as a LEO is greatly diminished.
The D/A's office really doesn't like to lose cases because of jerk cops, so those problems usually get sorted out over time.
I posted, for a limited time, on my home page the text of the petition I submitted to toss a speeding ticket in 2003.
I might well have been speeding, but, it was outside the jurisdiction of the officer that wrote the ticket by about 3 miles, he lied about the mile marker he put down on the ticket (which indicated the ticket occurred 5 miles back, in his town), and speeding or not, I was not breaking the law as the law in Texas specifically states that unsafe driving is the violation and operating a vehicle safely above a posted speed is NOT necessarily a violation of the law.
The city attorney postponed my case and never brought it back up (2 yr statute of limitations). In reality, despite everything else I said, his speed trap sign was illegally posted and he simply didn’t want to risk having to revisit 2 yrs worth of tickets.