Art. 11.21. CONSTRUCTIVE CUSTODY.  The words "confined", "imprisoned", "in custody", "confinement", "imprisonment", refer not only to the actual, corporeal and forcible detention of a person, but likewise to any coercive measures by threats, menaces or the fear of injury, whereby one person exercises a control over the person of another, and detains him within certain limits.
Acts 1965, 59th Leg., vol. 2, p. 317, ch. 722.