There’s an episode of LA Law that I’m after.

One of the subplots was a case where a man was accused of raping an 18
year-old. The defense attorney had her dress up the same way she was
from a photo taken that night, but the man was found guilty on a
lesser charge.

Which episode is this, and where can i get a copy?

Hi markabe-ga,

Thanks for your question. I remember this episode very well. 

The title of the episode was "The Gods Must Be Lawyers." The episode's
number is 97 and it aired on 2/21/1991 in the show's 5th season. Wayne
Newton played the rapist's defense attorney. His client is charged
with several counts of rape. Although, he manages to clear him of the
statutory rape charge using the tactic you mentioned, the jury still
finds the client guilty of rape.

The Gods Must Be Lawyers
http://www.tvtome.com/tvtome/servlet/GuidePageServlet/showid-183/epid-22815

L.A. Law Episode Guide
http://lalaw.theshagster.com/index.cgi?func=story&shownum=97

Unfortunately, neither this episode nor the show are commercially
available via VHS or DVD. The pilot of "LA Law" is available for
purchase, but not the individual episodes. The show does not appear to
be on any of the major cable stations--A&E had been running it for
some time, but does not currently have it on their lineup. It is
possible that a local station near you may air the show.

A&E Schedule
http://www.aande.com/tv/listings.cgi?channel=aetv&get=week

Search strategy:
I had seen this episode and remembered that Wayne Newton played the
lawyer so that helped.
Google search:
"wayne newton" "l.a. law"
"l.a. law" vhs
"l.a. law" dvd
"la law" vhs
"la law" dvd
Also checked amazon.com; www.bn.com; www.ebay.com; tvguide.com and
http://www.tv-now.com

I hope this answers your question. If you require additional
information, please ask for clarification and I'll do my best to
assist you.

Regards,
luciaphile-ga

Woah! I had given up on getting an answer for this one. At least I
know which episode it was, now it's just a matter of finding it.

Well done! Hat very much in the "off" position.

Possibly episode 45 from season 3:

"Kuzak's tactics in a rape case draws his colleagues' scorn"
http://lalaw.theshagster.com/index.cgi?func=story&shownum=45