Clinton and Trump clash on them. Congress and some states have been trying to defund them. But no one can seem to agree on what it means to actually be a sanctuary city.
"Blue Lives Matter" bills that would increase the penalties for attacking police are popping up in states and Congress.
Technology is transforming the way police fight crime, making it safer for not only officers but also criminals and innocent bystanders.
Many police chiefs are ordering their officers to work in pairs. But whether that actually makes cops -- and citizens -- safer is up for debate.