Livelihood is frequently the reason why biases creep in. Independent labs tend to do better.

Here's a look at two different Texas crime labs. Compare and contrast, and see if you can spot the differences.

https://gritsforbreakfast.blogspot.com/2021/02/beyond-aid-to...

It starts with one pledging to:

   aid law enforcement in the detection, suppression, and prosecution of crime

whereas the other seeks to

    provide medical examiner and crime laboratory services of the highest quality in an unbiased manner with uncompromised integrity.

and goes from there.