How to trust someone who is constantly lying?

How can you trust a person who is always lying? I don't think there is a proper answer to that as I feel like that in itself is a red flag to not trust them. The only thing I could recommend would be to have open dialogue with them about how you feel like they are dishonest and ask them to work on it as you want to be able to trust them. If they aren't able to get behind that, then there isn't much more you can do. Hope this was somewhat of a help for you