There actually haven't been plenty of big cases where the main suspect turns out to be innocent. It's actually kind of rare.
There are quite a few wrongful convictions in our country but the vast, vast majority of those are of poor, black people. Not middle class white women. In fact, wrongful convictions of middle class white people appear to be quite rare:
http://theweek.com/article/index/228292/25-years-of-wrongful-convictions-by-the-numbers
http://www.theroot.com/articles/cul...ited_states_19892012_how_race_factors_in.html
http://www.innocenceproject.org/Content/DNA_Exonerations_Nationwide.php
Further, most of the wrongful convictions appear to me to be based on the investigations of one or two small LE agencies and often involve jail or prison "informants" in prison. That's not the case here.
In this case, the investigation centered quickly on TH, even while parallel tracks sought to explore all other, possible avenues. And the investigation hasn't involved one, podunk agency. It has has involved the following agencies:
Multnomah County Sheriff's Office, Gresham Police, Fairview Police, Troutdale Police, Portland Police, Port of Portland Police, Clackamas County Sheriff's Office, Clackamas County DA MCT, Multnomah County DA's investigators, Washington County District Attorney's Office, Washington County Sheriff's Office, Gladstone Police, Oregon City Police, Milwaukie Police, Canby Police, Lake Oswego Police, West Linn Police, Vancouver Police, Hillsboro Police, Beaverton Police, FBI, DEA, ICE, Secret Service, DOD Defense Criminal Investigative Services, Oregon DOJ, Oregon State Police.
http://www.oregonlive.com/portland/index.ssf/2010/07/mcso_progress_continues_in_sea.html
I think it would be highly unlikely that the focus of the investigation here is incorrect or that some crucial key to this case was missed by 26, separate agencies.