Cops are going door-to-door in an American city again, only this time at least they are knocking on doors instead of knocking them down.

The most recent example of a police-state presence is developing even now in Sanford, Fla., where neighborhood-watch participant George Zimmerman is on trial for murder for the death of teenager Trayvon Martin.

While the media has portrayed Zimmerman as white, he actually has a Hispanic heritage, and Martin was black.

Police say they fear the backlash from the community which could develop at the point the jury verdict is delivered. Los Angeles had days of rioting when the Rodney King verdict came down.

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So Sanford Police Chief Cecile Smith confirmed officers are going door-to-door talking to people.

"Our worst fear is that we'd have people from outside the community coming in and stirring up … violence," he said.

Authorities are seeking help from local pastors in their campaign, too.

Police did a lot more than knock in the aftermath of the Boston Marathon Islamic terror attack.

There, they burst into homes with guns drawn, ordering residents out while they searched.

Commentators said while homeowners there technically had the right to refuse a request for a search if officers didn't have a warrant, "it seems unlikely that many residents of Watertown felt like exploring that particular legal nuance by refusing the policy entry."

Probably the most impactful example of police invading homes was in New Orleans during hurricane Katrina. There, officers simply went into homes and confiscated weapons they uncovered.

Thousands of weapons – legally obtained and owned – were simply grabbed from citizens after New Orleans Police Superintendent P. Edwin Compass III announced, "Only law enforcement are allowed to have weapons."

Just to make sure the message was loud and clear, the city's Deputy Police Chief Warren Riley told ABC News: "No one will be able to be armed. We are going to take all the weapons."

Then they did exactly that.

One man at a post-Katrina meeting assembled in conjunction with the National Rifle Association said, "The bottom line is this. Once they did it, they set a precedent. And what we've got to be sure [of] is that the precedent stops here."

In a series of videos, the National Rifle Association has documented the stunning weapons grab by police in New Orleans, assembling videos that show them physically taking weapons from individuals, including one woman who was stunned when officers threw her against her kitchen wall because she had a small handgun for self-defense.

The not-to-be-forgotten images, Part 1:

Part 2:

Herb Titus, a nationally known constitutional attorney and law professor, told WND government's claim always is that such draconian powers will only be used "in an emergency situation."

But there are so many “emergencies,” he said, that "all of our rights are in jeopardy."

"It's typical of the government to do this, typical of this age. You see the government believes it can make the decision for you better than you can make it for yourself. There's a lot of this from the Obama administration," he said.

The result? Government "as our master, rather than servant," he said.

Jack Cashill's book on this case, "If I Had A Son," will be available soon after the Zimmerman trial is over. His investigative-reporting skills shine in his many books – see them now in WND's Superstore