The main theory being he was murdered by a hit-man hired by his widow Courtney Love. Love's own father holds on to the belief that his daughter played a roll in the founder of grunge's untimely death.
The theories-
It was a well known fact at the time that Kurt was going to divorce Courtney as she was not in love with him and was rumored to be cheating on him on a regular basis with a band member from the smashing pumpkins. Courtney stood to gain a lot more fame and money from becoming the widow of Grunge instead of the divorcee of Grunge. It is documented that before his death, Kurt was attempting to write Courtney out of his will. He never got the chance.
Eldon Hoke, singer of a band called the Mentors, claimed he was offered $50,000 by Courtney to kill Kurt in December 1993. On March 6, 1996, Hoke was administered a polygraph test by Dr. Edward Gelb, who is one of the country's leading polygraph experts and teaches the advanced polygraph course for the FBI. Hoke passed a lie detector test with 99.7% certainty that he was telling the truth. Eldon, also known as "El Duce" claimed on the documentary "Kurt and Courtney" that he was disappointed he didn't do the deed but he knew the man who did murder Cobain. A week later "El Duce" was killed in a mysterious train accident.
According to police reports there were no finger prints on the shotgun,the shells or the pen that wrote the suicide note. Cobain wasn't wearing gloves so how he avoided to get his prints on any of the items around him remains a mystery.
The suicide note was more of a rambling about his disappointment with himself in regard to the icon he and his band Nirvana have become. Many people believe the note was announcing his intentions to leave the band. However,the last 6 lines which are written in a different handwriting refer to the suicide.
In the weeks leading up the death Kurt convinced many people he wasn't suicidal including the doctors in Rome,the staff at the exodus rehab clinic in L.A and his best friend Dylan Carlson. Carlson bought the shotgun on March 30th . Kurt convinced Carlson that he needed the gun for protecting his house against unwanted guests. The only person that suggested it was suicide immediately after the death was Courtney. Which went against the opinions of the people closest to Kurt.
After Kurt escaped from the exodus rehab clinic Courtney hired a private investigator to locate him. Tom Grant did his best to locate Cobain. However, after the death he became the conspiracy theory chief and told everyone who would listen that he firmly believed Courtney Love only hired him to make it seem like she was concerned. When in actual fact she didn't even bother to return to Seattle to look for him.
The police report states a stool was used to block a side door from the inside. However,there was no access from the outside through that door. Surely Cobain would have known this and not bothered to barricade the door.
At the time of his death Kurt had 3 times the lethal amount of heroine (225 mgs) in his system. Medical experts are quoted as saying Cobain wouldn't have had the capacity to lift a shotgun let alone use it.
The rumor mill continues to churn out interesting theories about this one. Will we ever know who killed Kurt Cobain? Only time will tell.
Thanks,Kris.