"Marshall Hennington, the founder of New York-based trial and jury 
consultancy Hennington & Associates and a clinical psychologist, 
said he was not so much surprised at the jury being deadlocked twice as 
at the judge sending them to continue their discussions after they had 
already been deliberating for an unusually long time. He said the judge was “teetering on the brink of coercion” by 
ordering the jury to deliberate for a third time after so many days. “Does the judge respect their decision? There are some legal issues 
here and the judge runs the risk of being seen as biased. If they do not
 have enough evidence to decide beyond reasonable doubt then he may be 
considered to be forcing their hand,” said Hennington. But he pointed out that ruling a case a mistrial is tantamount to 
saying the jurors did not fulfill their obligation to make a decision 
one way or the other."
http://www.theguardian.com/us-news/2015/may/07/deadlocked-etan-patz-jury-sent-back-third-time-legal-experts-dismay