Yes they can be. You ask the average 65-year-old white person why they won't let their grandbabies marry a black person and they'll say, "because their crime rate is higher". Well that is true! Wanna know why? Because people of color (POC) get pulled over more for speeding, they get put in jail for longer for the same crimes. Sad but true that is what it is. In reality, it is not illegal to put a POC man in jail for more time than a white man for the same crime.
Nowadays, every public official is, in a way, corrupted. They are often swayed by biased reasons, and often make decisions based on stereotypical observations. But who doesn't?
I believe that this is a silly question, comparable to, "Why is there life on earth?". Although Utopia is impossible, the point is to strive for it. So, yes, police officers can be racist. But did we expect otherwise?
Even though the colored are more likely in due process for a crime, it is absurd a colored person will be judged immediately because of others' past descretions. Leaving the enforcement official to dictate crime based on skin color is exactly why desegregation tool part in the united states of America, so such discretion won't take part anymore, in order for equality for others. If it wasn't right for services to not take in colored, how is it right for the officials to determine who is more likely to have commuted a crime? Biased opinion is, out of the question, part of what makes humans be classified as individuals, but if it is the law, no racism should ever be permitted to conclude of obstructive behavior. The two only reasons colored are more susceptible for crimes is their neighborhoods they had to fight over with in order to accomplish a seemingly superior status from a poverty stricken condition that has put into affect ever since segregation, and the fact the officials is looking towards the colored than the whites whose crimes may already came into play but isn't reported or investigated due to more qualified suspects of interest.
So to answer the question, yes police officers can be racist. But if we are going off of who can be racist and not who is, then you should just assume every person who is not your race that you meet is racist and hates you because you are not their race. But believing that cops are racist because they are white and a guy they killed is black is more racist than anyone else could ever be. The cops are your friends. They protect you. If you wanna live without the police covering your ass for just a few hours just watch how quickly everything you've ever known burns to the ground to arsonists, watch how quickly your daughter is raped by a rapist and watch how quickly everyone you love is killed by a murderer