I can’t imagine a law firm not getting one. Do you have an online contact form? As a legal practice, wouldn’t you want to go the extra step to secure any communication sent to you via that contact form? The SSL certificate has multiple uses for your web site domain including accepting payments, securing surveys and securing communications.
To accept payments on your web site with CenPOS, most, if not all, law firms prefer to embed the payment object onto your own web page so the client never leaves your web site. This is achieved with an iframe, a single line of html that you place on your web page. Although the CenPOS object is secured, if you do not have an SSL certificate, the little lock will not appear at the bottom of the web page, leaving your client to wonder about security. You could also create a pop up box and it would display a CenPOS URL with the secure lock.
See also Which SSL certificate should I choose?