It’s not uncommon for a criminal jury to be close to a verdict, but to have a few hold-outs. (See Do criminal jury verdicts have to be unanimous?)
If, after the prosecution and defense have rested their cases and made their closing arguments, the jurors’ deliberations have stalled, a judge might step in. Judges can’t force juries to reach verdicts, but they can apply a little pressure when the jury has deliberated and reported back that it’s at an impasse.
When a jury claims that it can’t reach a verdict, a judge may employ the “dynamite charge,” intended to blast the jurors out of their deadlock. It’s an instruction that urges the jurors to try to come to a verdict; it usually tells them to examine the case’s issues and reconsider their opinions and those of other jurors. But judges must be careful not to go too far—appeals courts will overturn convictions where judges have coerced juries into verdicts.