A word, gesture or expression for a confident "shrug"

I am trying to look for a word, gesture or expression that represents a state of confident not knowing. So far I am using a shrug for this but when used often it starts to come off as very apathetic which I definitely don't want. I have found gestures for being confused, uncertain etc but they don't quite fit because they don't capture the vibe of knowing confidently that you don't know the answer. Consider when being questioned and you want to make it very clear that you are certain you don't know the answer, not that you couldn't care less. The only thing I have thought of so far is a head scratch but this again doesn't communicate much certainty.

Example 1:

The policeman looked sternly down at John, "Mr Smith, where was Nigel between 4 and 6pm on Sunday evening?"

John shrugged, "I swear I don't know officer, I was at a work function until 7pm that night."

Example 2:

"Do you still love me John?" asked Mrs Smith.

John shrugged, "Honestly, I don't know anymore."

I don't think that there is an expression specifically for shrugging. 'Shrugging' falls into words like run, speak, wave, jump, etc. You have to add separate words to give an action context.

For your first example: John shrugged with a smirk, "I swear I don't know officer, I was at a work function until 7pm that night."

For your second example: John sullenly shrugged, "I just don't know anymore."

I think you might be looking for a “nothing-to-hide” gesture. It shares with the shrug an open palm attitude, but the shoulders don’t rise up:

_{Image source: Dreamstime: A young man shows his two bare hands showing nothing to hide}

“I honestly don’t know.”

That’s the gesture. I don’t think there’s a single word to describe it though. You can get some ideas for phrasing by searching ”hands” “nothing to hide” “gesture”.

Here’s one result:

Illustrative gestures. Everyone produces gestures spontaneously and unwittingly as they speak. We may seldom think of our gestures consciously, but in practice we use them with great efficiency and sophistication to cover a surprisingly wide range of communication.... These include: Open palms at an angle. Gestures with palms showing (tilted to a 45 degree angle) signal candor and openness. When being truthful or forthcoming, people tend to use open gestures, showing their palms and wrists and spreading hands and arms away from their bodies, as if saying: “See, I have nothing to hide.”
_{Source: amanet.org — When Leaders Talk with Their Hands}

For dialog, this might suggest something like:

John, palms outstretched, replied, “Honestly, I don’t know anymore.”

Palms upturned, John offered his alibi: “I swear I don’t know, officer; I was at a work function until 7 PM that night.”

You are right. The shrug displays lack of concern when concern is just what should be displayed. I agree with cruthers in his looking in the eye. Nothing else could get the understanding across in such a compact and assured way. A long, telling, direct look in the eye along with any kind of speech would do. That would say "I don't know what you mean 'wink wink" Message transmitted.

While this is not a "word, gesture or expression" it is an action that gets across the meaning the OP was asking for.