Do speaker cables need a burn in period?

"In a court of law would this prove burn in is not a fallacy but true?"

As long as there is reasonable doubt, no.

Circumstantial Evidence

Information and testimony presented by a party in a civil or criminal action that permit conclusions that indirectly establish the existence or nonexistence of a fact or event that the party seeks to prove.

Circumstantial Evidence is also known as indirect evidence. It is distinguished from direct evidence, which, if believed, proves the existence of a particular fact without any inference or presumption required. Circumstantial evidence relates to a series of facts other than the particular fact sought to be proved. The party offering circumstantial evidence argues that this series of facts, by reason and experience, is so closely associated with the fact to be proved that the fact to be proved may be inferred simply from the existence of the circumstantial evidence.

I doubt that proving, or disproving, some cable falling apart or sounding one way or another, would undergo the same mechanisms of establishing the conclusion as solving the bank robbery. Highway robbery, on the other hand...

I have an experience I want to share with you guys. Yes it also takes time to break in a new cable. When it is broken in then don't feel safe like that when you buy second hand. I have bought second hand speakers and cables around the country (Denmark). Listen to it before paying and later transport. In winther time and if the speakers and cables are exposed to cold weather something happend to them. I have a van where the storage room has no heat. Typical transport time below zero can be from 1 to 4 hours. The gear that has been exposed to these temperatures do change their sound characteristics. Speakers that sounded good suddently sounds terrible and need to break in again. The same goes for cables. Happy listening - to music out there :-)

Cables should always wear their winter jackets when going out in the cold.