A hung jury is a slang term for a hopelessly deadlocked jury in a criminal case, in which a decision on guilt or innocence cannot be made. Usually it means there is no unanimous verdict , although a couple of states don't require a unanimous verdict to convict. A mistrial will be declared by the judge in the case of a hung jury, and a new trial with a new jury is required. However, the prosecutor can decide not to retry the case.
The definition of a hung jury varies by jurisdiction. A jury may be counted a jury as hung if it failed to reach a verdict on any charge or on any defendant. Some jurisdictions only count a hung jury if the jury failed to reach a verdict on all counts or on all defendants. The number of counts affects the likelihood of a hung jury. As the number of counts increases, so does the opportunity for disagreement. So, the more counts, the more likely that a jury will hang on at least one of them. Local law should be consulted for the exact requirements for a hung jury in your area.