You'll have to hold the button down in order to remain crouched. Movement in this position requires multiple buttons to be pressed at the same time. Using a weapon requires you to hold one button to raise the firing arm, and another to fire. Try to move in this position and you'll discover that you need the dexterity of a concert pianist in order to operate effectively. The ability to toggle between stand and crouch, or to keep the weapon arm raised, would have made a world of difference in the ability to control this game.
Many adventures simply have too many extremely difficult anti-logic puzzles included.
In Cold Blood does it's best to retain some semblance of logic, so you won't be required to do anything TOO unusual in order to succeed. Sneaking up behind enemies and disabling them is more important than assembling inventory items in odd combinations or running in with guns blazing. Overall, the game is good but could have been much better. Movement should have been much more slick and easily performed. Mouse control would have helped immensely.