§ 136.780 Evidence

Here's a plain English summary of this rule.

When a criminal trial has two parts, one to decide guilt and another to decide the sentence, the jury doesn't have to start from scratch in the sentencing part. Anything the jury already heard or saw as evidence during the trial can also be used when deciding the sentence.

This applies whether the case is decided by a jury or, if the defendant gives up the right to a jury trial, by a judge alone. Either way, the same evidence from the trial phase carries over and can be considered again during sentencing.

In simple terms, this rule saves time and avoids repeating the same evidence twice. The people deciding the sentence get to use everything they already learned about the case, instead of having witnesses testify all over again or evidence get presented a second time.