Can DOT legally search my backpack, even if it's on me when he searches my cab?

I believe the question should be 'can they search my cab' and I believe the answer is yes and no. Removing your backpack, or anything else while they search your cab would certainly raise suspicions.

According to dieselbear:
"Basically there is three ways for a search. 1) Probable cause, i.e. smell marijuana, or a drug detection K-9, 2) consent search or 3) a search warrant signed by a judge."

I've never encountered it and whether or not I consented would depend on the circumstances though I would likely not consent.

If you have nothing to hide it's probably easier (quicker) to consent but standing up for your rights is right.

That said, I cross the border often and those guys can search your cab, your pockets and anything else they want.

 

From my understanding without probable cause of a crime already being committed then no... They can look in the truck but cannot open any cabinets bags or "ruffle" through your belongings....
Source road dog radio had a lawyer on one of there shows and a very similar question was asked by a driver/caller

 

My guess it's a firearm... Probably for protection... What's everyone else's guess.. maybe guy comes along and tells us and we get to see who guesses right

 

Cab, cargo, and you as the operator. It's not a personal vehicle. I'm not arguing with anyone else's opinions on rights or wether I think it's right or not. Just that I....Personally...Think they can search whatever the hell they want with a Commercial Vehicle, without rhyme or reason. If anyone wants to post the actual FMCSA rules, I'd be happy to check it out.But where I live, after being pulled over by DOT, there were no requests. And even in a day cab,they invited themselves in.Hell they even went through my lunch box. Personal rights are few in a Commercial Vehicle nowadays.

 

And this is why they do it drivers don't know better... And nope can't show you in the regs but you also cannot show me in the regs where they have permission to go through my personal belongings.... I ain't t got nothing to hide and would even give them permission... Once at the border patrol station north of Laredo... They made the comment smells like marijuana I then told them your welcome to search the truck if you like... He said "oh really" then waved me on by think I caught him by surprise

 

Yeah. I notice they have many of what some of us refer to as "Grey Areas". Where the DOT manipulates what is or isn't said to suit whatever they feel like doing.

 

I haven't been able to find one. You'd think it would be easy find if it existed. Absent any rule giving them permission to ignore your rights I'd say there isn't one.

I quoted dieselbear, don't think he's here anymore but his name is what he does(or did) so he should know. Another one who used to post here as Trooper One said the same.

This is from a landline article:
The law itself
"Remembering the ins and outs of search and seizure law may seem tedious, but there's one thing to keep in mind - almost all of it can be boiled down into a few basic guidelines.

The founding principle of search and seizure law is the Fourth Amendment to the Constitution: "The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no warrants shall issue, but upon probable cause, supported by oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."

Think of the Fourth Amendment as the two sides of a coin.

On the one side, the amendment protects against unreasonable searches wherever there's an expectation of privacy - and in almost all situations, the inside of your truck counts. The flip side of that coin, however, is that if officers have probable cause, they can get a warrant, or in some very specific situations, conduct a search without a warrant, regardless of whether you give your consent (see related story below)."
http://www.landlinemag.com/Magazine/2006/May/News/Search-Seizure.aspx

That's enough for me.

 

His bag is full of panties that us drivers ain't got on.

 

There is an exception to the 4th amendment commonly known as the motor vehicle exception. In a nutshell, under certain circumstances law enforcement officers may search a vehicle, all containers inside a vehicle, and all containers removed from the vehicle by the occupants (including a back pack). Probable cause (the belief by an officer that it is more likely than not that a crime is or has been committed) must exist. The key is how the law enforcement officer articulates probably cause.
Google the search term <4th amendment motor vehicle exception> and you will find lots and lots of interesting reading on the topic that go into way more detail.