PHPSESSID, Googlebot and .htaccess

[John Smith]

Googlebot has been picking up numerous PHPSESSID name/value pairs in
URIs at my website, and this causes duplicate hits and wasted bandwidth.
I've since prevented PHPSESSID generation in my PHP script if
Googlebot makes the request; like so:

if(preg_match("/googlebot/i", $_SERVER['HTTP_USER_AGENT']) != 1)
//session code here

....but this doesn't stop the PHPSESSID requests from Googlebot because
they're already stored in its database, and it continues to request
query strings like this one:

<hxxp://mysite.com/getdetails.php?personID=I23&tree=num1&PHPSESSID=e0 489b957f2d336974ed7f2d71db2bab>

Therefore, I'd like to use modrewrite (in .htaccess) to permanently
redirect to the same page after stripping out the PHPSESSID name/value
pair..but I'm having great difficult in figuring out how to do this. (I
can strip it if it's the only name/value in the query_string, but not if
there are other name/values in there, as in the example above.) I now
wonder if it's even possible.

Yep, I've Googled exhaustively and you're better than me if you can find
a solution that way.
--
John