Through what procedures is it possible to be accepted for a job/training in the police?

Mister Grimm Asked: Through what procedures is it possible to be accepted for a job/training in the police?

I have been researching the state police applications for several countries in order to get familiar with the requirements, yet I still do not grasp whether I will be, in the future, capable of applying for the job without previous training (whether the application for becoming a police officer assumes in itself that you will be at first trained from the very basics) and/or without a specific degree (Law/Criminal Justice/Forensics).

To make matters more clear, I should probably explain that I am planning to complete a Bachelor degree in Linguistics, as I have sadly not found any appropriate degrees for myself in the area of criminal justice or forensics. However, I have stumbled upon general applications which have not mentioned any specific higher-education requirements from the applicants, and so I was wondering whether it would be possible for me to change jobs in the future to train and work in the police, despite my education and most probably career initially being something completely different and unconnected.

Thanks in advance for any replies!