What usually occurs at a housing court trial? I am going to evict tenants from prior owner and they have filed complaints with hpd. I closed in November and they did not have a lease with the former owner. I asked them to leave in January or pay and they refused to pay

Depends on what the charges or violations are?

What date did you take possession of the house? Did they have a lease with the former owner?

If you're moving on this fairly quickly you should have nothing to worry about.
If you've owned it a long time and let this situation go on without doing anything (legal and in writing) then there may be things you could be held liable for.