Sexual preference is biologically determined but sexual preference can be changed. Sexual orientation, determined early in life, may or may not match sexual identity, which can change over time but what if people choose dead body as a sex partner? Yes, you read correctly, dead body.
Necrophilia, also known as necrophilism, necrolagnia, necrocoitus, necrochlesis, is sexual attraction towards or a sexual act involving corpses. It is a pathological fascination with dead bodies, which often takes the form of a desire to engage with them in intercourse. Though prohibited by the laws of many countries, there have been many reported cases of necrophilia throughout history.