Is it the anxiety of not being sure or rather a principle against deduction based on clues that makes you so vehemently stand against concluding without concrete, irrefutable evidence?
Neither. It is a core tenet of rationalism (the idea that reason is the chief source and test of knowledge), an epistemological concept so important that without it, there would only be blind faith and dogmatic beliefs.
Theism aside, crimes are usually solved using the type of concluding and hedging bets that you are against.
The one key distinction between forensic criminology and academic discourse is the standard that they are beholden to. As you implied, there are often many holes in the deductive reasoning of a criminal investigator, which leaves their case neither 100% concrete nor irrefutable, and false positives can and do occur. However, in a court of law, those holes are acceptable as the prosecution only requires enough evidence and deductive reasoning to find the accused guilty beyond a reasonable doubt. This meant that all you have to do is convince the judge/jury that your case is more solid than that of the defence.
This is not the case in argumentation. In constructing a logical proof, one must ensure that each premise is valid and that they all connect to the conclusion, as any holes would instantly render the whole thing moot.