My understanding (I based this off of my father's opinion, he has been a CEO for 30+ years, and a friend who is an HR guy at startups) is that the 'normal' way of doing things is getting the reference at your current employer after the offer is signed by everyone.
Startups sometimes don't follow this convention, but that shows a lack of maturity.
I can give a half dozen former bosses and co-workers as references at any point in the interview process. I can also give current co-workers at any point in the interview process. But I'm not giving up my current boss's phone number until I have an offer in writing.
If the new company can't decide to hire me or not without talking to my boss, they're screwed anyway. Most large established companies don't allow supervisors to give much of a reference. My father's policy (coming from HR) was that if someone asked him for a reference, all he would give was 'Yes that person worked here, yes that was his title'. That's it. Nobody will give a negative reference because if the other company decides not to hire, the employee might sue you for submarining their chances at getting employed elsewhere.
So if you are relying on what the current supervisor thinks of the candidate to screen, you are in for trouble anyway. Nobody gives honest (negative) references.
Startups sometimes don't follow this convention, but that shows a lack of maturity.
I can give a half dozen former bosses and co-workers as references at any point in the interview process. I can also give current co-workers at any point in the interview process. But I'm not giving up my current boss's phone number until I have an offer in writing.
If the new company can't decide to hire me or not without talking to my boss, they're screwed anyway. Most large established companies don't allow supervisors to give much of a reference. My father's policy (coming from HR) was that if someone asked him for a reference, all he would give was 'Yes that person worked here, yes that was his title'. That's it. Nobody will give a negative reference because if the other company decides not to hire, the employee might sue you for submarining their chances at getting employed elsewhere.
So if you are relying on what the current supervisor thinks of the candidate to screen, you are in for trouble anyway. Nobody gives honest (negative) references.