Veronica's Testimony In The Echolls Trial

When Veronica is being cross examined by the defense attorney in the trial, he asks her if it's true that she's being treated for a sexually transmitted disease. How would he have obtained this information and how is it pertinent to her testimony? Health information is private between doctor and patient and there are strict laws protecting this information. No lawyer would have access to this information without a warrant and I can't see how a judge would issue a warrant or what grounds Aaron's defense attorney would have for requesting one for V's health information? This appears to be a very weak plot point in an otherwise strong episode and season.