Surely they can, as long as they don't allow their faith to trump the evidence. But in the case of evolution, it's perhaps a bit similar to expecting the liberal media to be "unbiased" in their reporting. It's theoretically possible, but not likely.
There is one scientist who is an outspoken Christian that I would trust on this issue, Dr. Francis S. Collins, the who led the Human Genome project. He has written on the subject of evolution and creation, and has no problem accepting evolution for the role it has in separating the species.
I agree with you regarding Dr. Collins. I understand he is a "recovered atheist." :^)
I suppose other trustworthy "outspoken Christians" who have been scientists would include such notables as Gregor Mendel, several Jesuit astronomers after which 12 of the craters of the Moon have been named, plus Isaac Newton, and -- in his strange way -- Albert Einstein; and the list goes on....