Not always. The mass murders are generally mental illness related, but in "normal" murders, arguments, drug deals, and robberies are popular circumstances. Read here:

FBI — Expanded Homicide Data Table 10

I agree with you about murder being murder, however you don't have to be mentally ill to commit it.

Given the number of crazy people I encounter on a regular basis, I think better access to mental health resources would probably be a good thing. And everyone knows no good can come from sporks.

More interesting reading here:

FBI — Expanded Homicide Data Table 8

FBI — Murder

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.