Jurors deliberated for 52 hours before a judge declared a mistral.
Dugan said tensions in the jury room complicated matters.
"People were frustrated. People missed their home. People missed their kids. It was a number of things and it finally all boiled up," Dugan said.
Prosecutors are working to rebuild their case for another trial.
A different juror last week expressed concern over the prosecution's lack of evidence, and said he didn't find Cosby's accuser to be credible.