Hummm..I think it might be helpful to review just what is Circumstantial Evidence versus direct evidence....and it appears this particular case is based mainly on circumstancial evidence NOT direct..NO ONE saw Brad move her body, no one saw Brad, strangle her, no one has a video of him doing either of these things...However there is a long list of circumstantial evidence directly pointing at Brad..and no one else..
http://www.wisegeek.com/what-is-circumstantial-evidence.htm
Circumstantial evidence is evidence in a case which can be used to draw inferences about a series of events. It is also known as indirect evidence; the opposite is direct evidence. Circumstantial evidence is an important part of any criminal trial, and both sides in a trial will generally try to find circumstantial evidence to support themselves. Contrary to popular belief, it is possible to obtain a conviction with the use of circumstantial evidence, if it is backed up by corroborating evidence and other factual information.
I am sure there are some who NEED direct evidence in any trial..however it is NOT neessary in order to obtain a conviction....
My list of a few of the circumstances
1)Brad last one to see Nancy alive
2)Brad in possession of items he should not have had..i.e. keys, phone, computer, necklace
3)Brad delay in calling about her missing status
4) Brad's out of character activities that particular morning
5) Brad's hx of controlling behaviors of his wife and children
6) Brad's explanations being shown to be somewhat OFF
7) Mysterious missing items of clothing ala 2 lefts of jogging shoes, his shoes
8) Activities in the garage that morning by 645AM..neighbour sees door open which was unusual
9) The state of Nancy when found..no pants, underwear, no poneytail, no hat, no necklace, no shoes and her bra all askewed as if put on after the fact..
10) No credible witness seeing Nancy leaving her house that morning all dressed for jogging
11) Well documented testimony how Brad treated Nancy...
12) Brad's losses IF divorce went thru..Money was very important to him..but I think it was the Control factor too
13) Brad's disregard to nancy's family after death of his wife
14) Bug evidence showing high possibility she was dead before he ever went to HT
15) Hx of Brad reading her emails and possibility of text messages
16) theres more..but the most important item is..WHO ELSE had the opportunity, means and reasoning to do this?