The big difference between Cosby's first and second trials, IMHO? The same judge

in both trials only allowed in ONE corroborating witness the first time -- and FIVE this time.

Also, of course, there is #Metoo.

https://www.cnn.com/2018/03/31/us/bill-cosby-trial-differences/index.html

Judge Steven O'Neill ruled at Cosby's first trial that prosecutors could feature testimony from one other woman with a claim similar to Constand's.

Kelly Johnson testified that Cosby gave her drugs that incapacitated her and then assaulted her. Prosecutors argued that her testimony showed that Cosby's actions were part of a concerted pattern and so, in Constand's case, were not simply a mistake.

What's happening now: For the retrial, O'Neill ruled that as many as five additional women with similar accusations against Cosby may testify against the comedian.

Among them is model and reality TV personality Janice Dickinson, who has been subpoenaed to testify at the second trial, a source close to the case said. Dickinson said in a November 2014 interview that Cosby sexually assaulted her in 1982 after the two had dinner in Lake Tahoe. At the time, Cosby attorney Martin Singer called the accusation "a fabricated lie."

But why did the judge change his thinking on "prior bad acts" witnesses? O'Neill did not provide a detailed explanation for his decision.