How judge decides whether signature is forged or genuine?

Dear Experts,

I request only experienced advocates to help on this please.

My uncle has filed a suit against me by producing a forged unregistered will of my grandmother

I have my grandmother passport and also copies of registered documents obtained from sub-registrar office. These documents clearly indicate my grandmother signature & thumb impressions.

Now even a layman can identify that the signature on forged unregistered will are fake. It is very very crystal clear & evident.

Such being the case, I want to know whether the Judge will be able to take note of this by visually comparing the signatures available on passport & other documets with the forged will and take a decision ?

Or is it mandatory for us to sent the forged will to forensic laboratory for expert opinion ? I am told expert opinon is not binding.

So in such case - which is the best method for me to help the Judge to take note of this forgery ?

Kindly help by answering.

Thanks