Police cannot come to your porch and conduct a search.
In recent years, the U.S. Supreme Court moved away from the issue of property rights to determine whether police could conduct a search without violating the Fourth Amendment. In other words, a doctrine such as the "open fields", where large tracts of land with open fields even near the home were free for police to enter, though unlawfully trespassing, to observe and use those observations to support criminal cases. Similarly, the "plain view" doctrine allowed police to use observations that it obtained from any Fourth Amendment recognized vantage point, except actually physically entering or intruding upon the curtilage around a house or the house itself (flyovers were also o.k., even if over the curtilage or house to get information).
However, on March 26, 2013, the U.S. Supreme Court drew a line in the sand as to how far police could go to conduct searches outside the home without requiring a warrant or probable cause to do so. In Florida v. Jardines, the Court determined that police could not approach your front door, porch or other area inside the curtiage around the home and have a drug-sniffing dog give a whiff or two to determine whether narcotics lurked inside. This case adds a somewhat rare contemporary point on the civil liberties side of the invdividual vs. collective ledger..
Under Fourth Amendment jurisprudence, the U.S. Supreme Court often permitted police to use observations when present where any civilian could lawfully observe cirminal behavior because police should not be hampered in crime detection when present where anyone else could be. Until now, the only real question was whether, under the earlier Katz decision, whether there was an objective and subjective reasonable expectation of privacy in the area or thing searched. Anyone can ordinarily come to your front door and ring the bell or knock for any legitimate purpose without violating your expectation of privacy or the law of trespass. However, here the Court stated that, while police can knock on the front door in the hopes of even interviewing the occupant or consenting to entry, and while doing so even use observations of illegal behavior against its occupant, police may not simply conduct a search of the house from a constitutionally-protected area, i.e. the curtilage immediately part of or immediately beyond the home's boundaries without the occupant/owner's consent. There is a difference, the Court decided between knocking as any person can do and bringing trained drug-alerting dogs to the curtilage area to conduct a non-consensual search.
The Supreme Court reasoned that the reasonable expectation of privacy is not the only basis to determine whether a violation of the Fourth Amendment has occurred, but, rather it is additional to whether state agents have made an incursion in a constitutionally-protected area to conduct a search where the Fourth Amendment does not allow, such as the home. There is a customary invitation or implied consent in the United States (and probably most countries) to allow strangers to knock at the front door. However, there is no such customary invitation or implied consent to enter the same area to conduct a search within the meaning of the Fourth Amendment to the United States Constitution.
Under the Supreme Court's spot-on reasoning here, all searches conducted within the curtilage are illegal. So, police approach to the front door and porch to look all around it or to peer through the window would not be permissible. Also, police would not be permitted to be in that area and obtain the aid of any tools to conduct a search, which might be permissible if beyond the curtilage of the home.
So, one can expect the illegality of searches to cover all types of tools used for searches and detection under these circumstances within the curtilage of a home, absent police obtaining a search warrant. If these types of searches occur, the trial court should suppress evidence of the fruits of the search upon raising the issue properly under procedural law.
However, do not try to handle your own criminal case's Fourth Amendment issues. It is just as unreasonable as police behavior in Jardines as it is for anyone to think that they can defend Fourth Amendment violations in a criminal case without the aid of an experienced criminal defense attorney.