The way I was taught, I had to look for matted material, that would show no one has cleaned in a while the area in question, that includes sidewalk and 18″ into the curb during routing times of 8:00am-9:00am and 6:00pm -7:00pm.
Note: Any litter on property during routing time would be a violation during these hours, no matter how or when it got there. The remaining area visible from sidewalk, including front court yard and side of building/house also has to be cleaned as far as visible from the street.
If the place is dirty, you get the summons. Property value goes down with a neglected neighborhood, and it starts with garbage, litter, rubbish and debris showing up all over the place, including in front of homes of people, it just does not look good, bad for the neighbors, you know they don’t like it.
It also attracts diseases and rodents love it. If you are not aware on how the streets use to look in days of old, read Picking Up by Robin Nagle (good read).
Property owners are require to have their properties clean at all times. City and workers know this and should not bother you on windy days when a piece of paper falls on your property that day but leave it there for a few days and you have a problem.
Someone drops something on your property(drop-off): Call 311 and get it on record before the city puts it on record with a summons.
Don’t touch the drop-off, it has to be inspected by an Officer or Agent, any handling of the material would be contaminating the proof and cannot be used to issue summons.
Most summons could be written 24/7, but only served during hours of 9:00am and 9:00pm. check with 311 for time (s)
Links that might help.Keep in mind that this is my view and at no time am I claiming law, as I am not a lawyer. Always go thru 311 for official views of the law.