Could murderers be put to death by being strapped to their dead victims?

Answer 1

No, this form of capital punishment did not exist.

The most gruesome forms of capital punishment were scourging (being beaten to death) ad bestia (devoured by animals) which was a sentence to the arena where you were left at the mercy of predator animals, and poena cullei (penalty of the sack). The person was sown into a leather sack together with a dog, a monkey and a cockerel. This was the worse penalty because it stripped dignity more than the others and because you would not be given proper burial.

Other forms of capital punishment were; beheading (percussio securi), this was the most common form, burning at the stake (this was for arson, slaves who conspired against their masters, deserters and enemies of the state) strangling in prison (strangulatio) throwing a person from the part of the prison called Robur (precipitatio de robore) throwing a person from the Tarpeian rock (dejectio e rupe Tarpeia) and throwing a person into the river (projectio in profluentem). For slaves and non-Romans there was also Crucifixion (in crucem actio). Roman citizens could not be crucified.

Most people who were sentenced to death, especially for the most gruesome forms of punishment, were poor people. The rich mostly found ways of getting out of it or were treated leniently, except for cases of parricide, where even the most gruesome forms of death were not spared.

The Vestal virgins (the priestesses of the goddess Vesta) who were caught breaking their vow of chastity were buried alive.

There was also free decision of death (liberum mortis arbitrium) where you were allowed to choose the method of execution. This was in essence an order to commit suicide, which was preferable to other sentences because it spared the humiliation of a public execution, your property was not confiscated, and you would be given a proper burial.