I'm not gonna write down the many, many facts and details contributing to the murder theory. Just gonna name some things that have come to mind.
1. Kurt's sense of humor: Kurt had a very dark sense of humor. This is evident in songs like "I Hate Myself and Want To Die." While Kurt brought up suicide a good deal, he wasn't actually a suicidal guy who hated life. He mentioned in the "About A Son" interviews that he often looked depressed and angry when in fact he was in a good mood. This is just his natural expression. He liked to have fun, and if you watch videotapes of him with the band, you can see he's obviously a very humorous, light-hearted person, not the depressed, morose person he is often made out to be.
2. Kurt's relationship with Courtney: Kurt was very much in love with Courtney and defended her early on in the relationship. But as time went on, things began to change. Kurt, who was Bipolar, began to form a tumultuous love/hate relationship with her. He was on the verge of divorcing her, prior to his suicide (which would have lost Courtney a lot of his money).
3. Kurt's songwriting: I believe that two of his songs have messages singling out or referring to his broken relationship with Courtney. First, in "All Apologies" he mentions the lines "married/buried" in the chorus. All Apologies itself could be a song denoting his perceived failure in their relationship, perhaps his way of saying he feels its not working out. Kurt didn't like to express his thoughts and emotions upfront, and they often seeped into his songwriting and performances. Secondly, refer to the lyrics in "You Know You're Right," the last song Kurt wrote, prior to his death. The lyrics include "never speak a word again/I will crawl away for good"; this could reference his plan to divorce her. "No thought was put into this/I always knew it would come to this" could reference his increasing wish to leave the marriage.
More lines from the song:
- "I'm so warm and calm inside/ I no longer have to hide" Perhaps he felt happy of his plans to retire from music, and he'd no longer have to hide the fact that he hated performing (mentioned in the "suicide" note)
- "Nothing really bothers her/ she just wants to love herself" Again referencing the chaos of their relationship
- "I will move away from here/ you won't ever have to fear" Again, expresses his desire to leave Courtney and the music business.
"You know you're right" Perhaps Kurt is talking to himself with these lines, reassuring himself that his plans are the right ones. Or, possibly, a sarcastic attack at Courtney.
It seems a little suspicious that Courtney so vehemently wanted this song to NOT be released after Kurt's death. She performed a live version of the song, changing some of the lyrics as well. It seems Courtney had something to hide about this song....
4. Drug use: Many people have blamed Kurt's death on his drug use. However, despite his use, he was known for being anti-drugs. He stated this in the "About A Son" interviews. Kurt smoked marijuana recreationally, but only used heroin as a means of alleviating the pain of his stomach condition, caused by scoliosis.
5. Courtney's relationship with Billy Corgan: Before dating Kurt, Courtney had a relationship with Smashing Pumpkin's frontman Billy Corgan. While the details of speculation that Courtney cheated on Kurt with Billy when she dated him isn't fully known, this could possibly have caused a riff in the Kurt/Courtney relationship (also, it is possible that Billy was a factor in Courtney's possible desire to kill Kurt). Courtney and Billy have recently been seen together.
These are just a few lesser known opinions (strictly opinions and theories - the truth is yet fully known) of mine. I hope they've offered insight.