I found this post by Karen Franklin about the importance of an expert witness being a good teacher. She notes that many experts come off poorly to jurors, due to presenting oneself as arrogant, whishy-washy, defensive, etc. Then, referencing an article by trial consultant Richard Gabriel in The Jury Expert, she highlights several styles and strategies that allow for an expert witness to form a connection with the jury, primarily as a result of being an effective teacher of their area of expertise.
I recommend this post (and the article) to anyone who has to testify as an expert witness. I would go one farther, however: it is not just the jurors who benefit from an expert being able to effectively teach and communicate, but also the attorneys and the judge. In many cases, it is not just the psychological expertise that the expert needs to be able to discuss, but also the relationship the psychological findings have to the legal question being asked. This is because some of these issues do not arise very often, and the legal participants involved are not all that familiar with the specifics. I have personally found that, at least on the Federal level, both attorneys and judges have been very receptive to my status as an expert witness, often asking questions about all sorts of related issues in an attempt to understand the issues involved. This has been encouraging, to say the least. Of course, it helps if one follows the advice provided by the links, so click away and check it out.