Bad news for Beliebers -- and especially for Justin Bieber himself.

The Los Angeles County Sheriff's Dept. is recommending that the boy wonder be prosecuted for allegedly spitting on his neighbor ... and the outcome doesn't look good.

TMZ reports that the Sheriff's investigators plan on presenting their investigation results to the Los Angeles District Attorney for review, and that if history is any indication, charges will likely be filed against the 'Believe' singer.

While the investigation isn't complete yet, insiders say that the case is pretty cut and dry against the singer. They also note that his recent history of misbehavior and mishaps, including lunging at a paparazzo, driving irresponsibly and being photographed with weed -- none of which he's been prosecuted for separately -- can be used against him in court. The sheriff's office says it's pretty typical: small crimes and offenses that have a lot of potential to eventually escalate into something truly terrible.

What's more, sources in the Sheriff's Dept. recommend anger management to control Bieber's outbursts and behavior, and not just because he's a celeb. They simply say that anyone with his recent pattern of behavior needs help keeping themselves in line to avoid much bigger and much more serious issues and crimes from arising.

C'mon, Bieber -- don't take after your buddy Chris Brown ... or even your pal Lil Twist. And speaking of the latter, stop lending that jerk your cars while you're at it.

Watch the Justin Bieber 'Beauty and a Beat' Video