I don't think "lie" is a fair description.
Perhaps be a little vague, but at the same time, you don't want to tip your hand.
If you are a defense attorney, and a good one (Of which I believe Harley to be), then you don't give the prosecution anything until required.
It is the job of the prosecution to prove beyond a reasonable doubt that someone committed the crime they are accused of. If for instance, I know for a fact that I have, during my discovery phase, perhaps found that one piece of evidence or testimony that will completely exonerate my client, you do it in court where the jury can hear it.
Of course there are times where you do certain things in chambers, but still, in general, if for whatever reason, you find the ace after the grand jury, you don't show it during statements to the public. You show it when it can take the prosecution completely off their game.