Three people have been jointly charged over the murder of Hutt Valley man Matthew Stevens.

His body was found near his white Toyota Corolla in thick bush on a steep slope off Paekakariki Hill Road at the end of last month.

A 27-year-old man and 27-year-old woman charged with being an accessory have had their charges upgraded to murder.

A 24-year-old man who is already in custody on unrelated charges has now also been charged.

All three will appear in court next Tuesday.