If a person could be totally objective, and this may not be possible, then they may ask some questions of them self. An example of some of these questions may be as follows:
If God did exist, and He had played a part in this process, then would I interpret this evidence differently?
If the interpretation of this evidence would have an effect upon my prestige as a scientist, or my acceptance by my peers, then would I interpret this evidence differently?
If the interpretation of this evidence would have an effect on my ability to obtain a job, or to obtain a government grant, or to obtain any financial benefit, then would I interpret this evidence differently?
If the interpretation of this evidence would have an effect upon my personal relationships, then would I interpret this evidence differently?
I think you can see where this is going. There are many ways that a person’s judgment can be compromised without outright forgery of the evidence.
I agree, it may be difficult, if not impossible to be completely objective when looking at evidence. But I'm pretty sure that most good scientists do a very good job of it. The ones who can overturn an established theory and account for all the evidence we have, plus make predictions about any new evidence would be automatically catapulted to the upper echelons of science, we would know their name as a household word, and they would win a Nobel Prize.
Newton is a name we all recognize because he was able to formulate his theory of gravitation, one that was so different from the established idea that he was ridiculed at first. Einstein came along and revolutionized even that theory, I'm sure you've heard of him. The scientists who first noticed the increasing complexity of the fossils in the geologic column and began to notice morphological similarities were almost all Christian. They came at the evidence with a definite Christian bent, and the science at the time was dominated by Christians, where it would have been safer and easier to ascribe their evidence to god, but it was obvious to them that what they had read and learned from the Bible could not be literally true based on the evidence. They weren't willing to accept a god who would trick and deceive them, and I guess that would be their biggest bias, so they had to follow where the evidence took them. They were not trying to overthrow religion or make god unnecessary, they were just seeing the evidence and realizing what it was saying, rather than what they wanted it to say.