References are an excellent way to confirm someone that someone did actually work at a particular place in a particular role and that they are not a total asshole. Beyond that, unless you know the reference well, I think they can be unreliably.
The reference knows the candidate and likely feels a much closer connection with them than they do with you. Assuming the candidate isn't an asshole, they will want to help them out by giving them a good recommendation. If the candidate was let go due to downsizing or such, the reference may even feel pressure to help the candidate find a new job.
So it's a great data point to have and as you say, it can help weed out the straight up liars.
But any 2 given candidates with 5 years at Acme Inc are not interchangeable. Some candidates are just better at programming (or some subset of it) than others, and I think employers try to find ways to predict that at interviews.
The reference knows the candidate and likely feels a much closer connection with them than they do with you. Assuming the candidate isn't an asshole, they will want to help them out by giving them a good recommendation. If the candidate was let go due to downsizing or such, the reference may even feel pressure to help the candidate find a new job.
So it's a great data point to have and as you say, it can help weed out the straight up liars.
But any 2 given candidates with 5 years at Acme Inc are not interchangeable. Some candidates are just better at programming (or some subset of it) than others, and I think employers try to find ways to predict that at interviews.