The way this handled varies from jurisdiction to jurisdiction.
I understand from previous threads here that in some states of the US, the prosecutor gets to decide whether lesser included offenses are put to the jury. For instance, I think in the case of the English nanny a few years ago, the prosecutor only put the most serious offense to the jury.
In other jurisdictions in the common law world, it’s up to the judge to decide if a lesser included offense should be put to the jury. That’s how it works in Canada.
The indictment just lists the most serious charge. Then, after all the evidence is in, the Crown and the defence can make submissions on this point to the judge, who then decides whether to instruct the jury on the lesser included offences.
If the judge decides to do so, the judge will start with the offence actually charged, then would explain the idea of lease included offences, and instruct the jury on each one in turn. It’s then up to the jury to decide which, if any, offence the accused is guilty of.
The usual example of lesser included is:
• Murder 1st degree - intentionally kill, with premeditation:
• Murder 2nd degree - intentionally cause death, without premeditation:
• Manslaughter - cause death by an unlawful act, but without intention.
The jury would first consider murder 1. If they find the accused intentionally killed with premeditation, they should convict.
If they conclude no premeditation, they should then consider murder
2. If they find intentional killing, they should convict.
If they find no intention, they then consider manslaughter. If they find the accused caused death by an unlawful act, they should convict. If not, they should acquit.
And, if they accept a defence, then they should acquit. For instance, if they conclude that the accused didn’t cause the death, or have a doubt about it, based on the medical evidence, they should acquit.