Please give a sample of an introduction on a paper on abortion.Specifically of mention would be law reform on abortion.

I think that you are probably going to have to compose
this on your own.  Yet, you probably could get many insights on how to write this here. 
I think that a good introduction on the topic would briefly address why legal reform on
the issue or even legal statements on the issue have been so challenging.  This would
embrace the idea of how the Constitutional issues of federalism, in terms of state and
federal government differentiation on the topic, and personal choice have have helped to
confuse and complicate the issue.  At the same time, I think that the introduction might
want to talk about how the issue has become so politicized that legal reform is very
difficult to accomplish.  Discussion of it being a "litmus test" or "hot potato" issue
might be relevant here.  I think that the introduction should probably close with what
you intend on proving in the course of the paper on the topic.  Along these lines, your
introduction should embrace a good understanding and feel of what is going to be
discussed in the paper.  In the end, this might be why you would have to compose this. 
You alone understand what your paper is going to address and prove.  The reader is going
to be led to this conclusion and your introduction would be a start on such a
quest.