I have never used crime date to evaluate a property or the neighborhood. Milwaukee is so block by block that I don't think data from a website can give you the information you need to decide. If tenants are questioning a neighborhood, I always recommend them to drive around at different times of the day and see what they think for themselves. As an investor it is also good to drive by and walk the neighborhood at different times of day so you can get a feel for it. I look for the follow when I decide on an area. How many people seem to be just hanging out? How many lawns aren't cut? What condition are the other properties in? What condition are the cars in? If I don't feel comfortable going to a property, I won't buy it for myself or manage it for someone else.
I've worked with some out of state investors and its hard to describe but there are some great pockets in the city that crime data would tell you to run from. Get out and drive around is my advice.