With Sunday's release of the Cosby deposition in Constand's civil case against Cosby by the New York Times and the unsealing of other documents in the case by the Associated Press, Castor has been discussing the old case with national and local media.
In the nearly 1,000-page deposition, the comedian admitted to inviting Constand, a former Temple University employee, to his Cheltenham home on the night in question. He admitted to giving Constand some Benadryl and said she took it willingly, and he denied giving drugs to women without consent.
Castor, who is running for D.A. again in November, told the Daily News: "I still think he needs punishing."
If he was in office, he said, he'd prosecute Cosby on charges of perjury, with these "ifs":
* If the statute of limitations, which is five years, is paused. Law-enforcement authorities didn't have access to the sealed deposition and "could not reasonably be expected to have discovered the violation," he said.
* If Cosby told "intentional untruths" under oath that is material to the outcome of the case. "Make a list of every material statement that he made" and compare it to what he's said outside of the deposition, Castor said.
* If the Montgomery County D.A.'s office has jurisdiction over the case. The alleged crime happened in the county, but the deposition was taken in the Rittenhouse Hotel in Philadelphia. If the Montgomery County D.A. lacks jurisdiction, Castor said he hopes someone will pursue the case. "I wouldn't presume to tell a prosecutor how to do their job," he said.
When Castor declined to file charges in 2005, he said, "that was all done by design."
The D.A.'s office "didn't have enough evidence," he said. "The best thing to do was to create an atmosphere that they [Constand and her attorneys] have the best opportunity to sue."
In other words, Cosby wouldn't be able to invoke his Fifth Amendment rights if there was no prosecution and would have to answer almost any question posed to him. But Castor believed that Cosby's downfall would happen a different way.
"What I actually thought was that he would be deposed and then there'd be a trial" and everything would come out, he said. Instead, Constand settled with Cosby and signed the confidentiality agreement.
On Twitter: @ReginaMedina