If in the moment of passion and unmitigated rage you attack and kill your spouses’ lover you will likely face voluntary manslaughter charges. This is classified as a homicide crime. Whereas murder is a capital offense that can warrant the death penalty, voluntary manslaughter is less severely punished because it is regarded as an “unintended” killing. This unintended killing is different from murder because you lack the specific intent or premeditation to kill; rather, you acted in a rash and dangerous manner that turned out to be fatal.
The fact that voluntary manslaughter is not as severely prosecuted does not mean that it is not taken seriously. A conviction for voluntary manslaughter under Penal Code Section 192(a) can lead to a sentence of 3, 6, or 11 years in state prison. Since this is regarded as a serious and violent felony, you will also incur a “strike” on your record for the purposes of California’s Three Strikes Law. This means that if you face any future felony charges, your penalties can double or lead to a lifetime sentence, depending on how may prior strikes you have on your record.