She has a good heart - so can nail down the facts part of the law - but I think she fails the legal background/theory kind of thinking required at supreme court and court of appeal - where questions of law - not the facts of the case - are being addressed.
The lawyers here can put it better - but I believe at appellate or higher courts - the judges are more concerned with legal issues - question like is Abortion Legal - rather than did you do an abortion (lower court).
Questions of Fact vis Questions of Law.
So bigger brains - are needed at Supreme court where they deal with more "academic" questions of law - and I don't think she has those credentials..to sit with likes of Prof Smokin Wanjala, Prof Ojwang, Isaac Lenaola and etc.
Because she is incorruptible - she dispenses the question of facts - very expeditiously.
Judge Mumbi Ngugi is a class of her own. Most likely she will never get further than judge, but on integrity she is above all others.