FREEPORT, Bahamas—A four-month investigation into the death of late Playboy model Anna Nicole Smith's son determined Monday that the 20-year old died from an accidental drug overdose.

A coroner's court ruled that Daniel Smith's death was caused by the "nondependent use of drugs," suggesting that he was not addicted to the substances found in his body and unaware at the time of this death that the mixture could be fatal.

The court, which said it was unlikely that criminal charges would be filed, said Monday's findings probably represented the end of the marathon case in Bahamas' court system.

Daniel Smith died in September 2006, just days after arriving here to be with his mother and new born sister Dannielynn.

The inquest into his death, which got underway in November, was ordered by Bahamian authorities when questions were raised about his death being a possible suicide or homicide.

An autopsy showed that Daniel Smith had ingested a lethal cocktail of various drugs, including methadone and antidepressants.

Anna Nicole Smith, 39, died in February 2007 in a Florida hotel room, just months after the death of her son. Her death also was later ruled an accidental drug overdose.