TVNewser has learned ABC News senior legal correspondent Jan Crawford Greenburg is leaving ABC for CBS News.

Greenburg, an Alabama native and mother of four, joined ABC News three years ago. Before ABC, Crawford Greenburg spent 20 years as a reporter for The Chicago Tribune, much of the time spent covering the Supreme Court. In 1998, she began providing legal analysis for PBS' "The NewsHour with Jim Lehrer" where she remained until ABC brought her on in 2007.

Insiders tell us CBS News Washington managing editor Bob Schieffer has been a mentor to Crawford Greenburg.

For CBS News, she'll continue to cover the high court. But she'll first have to sit out a non-compete clause in her ABC contract. Terry Moran will be covering the court, as he has done in the past, in addition to his "Nightline" duties for ABC News.

After the jump, Crawford Greenburg's goodbye email to her ABC colleagues...

As many of you already know, I am leaving ABC News for a position at CBS commencing January 1, 2010. It was a difficult decision, but I concluded I couldn't pass up the opportunity to broaden the focus of my reporting and tackle a wider variety of legal and political issues, including having a regular role on Face the Nation. I leave with the highest respect and admiration for all of you who are so integral to producing the kind of great journalism that enlightens viewers and defines our profession. There are too many people to acknowledge and thank here, but on a personal note, I'd like to give a special thanks to Ariane de Vogue and Dennis Powell, two dedicated journalists I was privileged to work with on the legal team. And as Charlie Gibson turns the anchor chair over to Diane Sawyer, I also want to acknowledge my debt of gratitude for Charlie's friendship and support---as well as his patience as this former print reporter transitioned to television and learned to say "bites," not "quotes," and "scripts," not "stories." As I move from a colleague to a competitor, I hope the friendships we have made will endure.

Jan