A more thorough explanation:

A nitroglycerine charge, also known as an Allen charge, is a supplemental instruction given by a judge to a deadlocked jury. This instruction is given after prolonged deliberations to encourage the jury to reach a verdict.

For example, in the case of Allen v. United States, the judge gave an Allen charge to the jury after they were deadlocked. The charge encouraged the jury to continue deliberating and to try to reach a verdict.

Other terms used to describe an Allen charge include dynamite charge, dynamite instruction, shotgun instruction, and third-degree instruction.

The purpose of a nitroglycerine charge is to prevent a mistrial and to ensure that the jury reaches a verdict.