+1
I am watching a movie (Sherloc Holmes) I have noticed a sentence:

God knows what they've been spraying on us all this years or putting in the water.

I wouldn't trust them as far as I could spit.

Did not understand the part of the sentence which is highlighted.

Can someone give me an explanation, please?
+1
DanilCan someone give me an explanation, please?
I wouldn't trust (someone) as far as [ . . . . ] is an idiomatic formula that means "I do not trust (someone) at all" or "(someone) should not be trusted".
.
I wouldn't trust him as far as I could throw him is a popular one. The one you quoted (I wouldn't trust him as far as I could spit) is another version of the same saying.
.
CJ
Comments  
Site Hint: Check out our list of pronunciation videos.
Thank you, Mr CJ. Very clear for me.
Regards
DanilSherlock Holmes
As shown.
CJ

Apparently the origin of this phrase relates to an item called a ‘spit’ which was used by customs men (like a rod to br pushed into bales of material) so that was the limit of anyone’s trust. Only as far as you could verify?

Students: We have free audio pronunciation exercises.

A spit is a long metal spike. Customs used one to thrust into bales of wool to check that nothing was being smuggled in the inside of the bale.

anonymous

A spit is a long metal spike. Customs used one to thrust into bales of wool to check that nothing was being smuggled in the inside of the bale.

It's fun to dream up imaginary etymologies. It's better, though, if they make sense—if you want to muddy the waters for everybody to no good end, that is. Please provide citations to support your claim that the expression "trust as far as one can spit" derives from this activity.