WHAT are the essential requisites of illegal possession of dangerous drugs that must be established?

On the other hand, the essential requisites of illegal possession of dangerous drugs that must be established are the following, namely: 

(1) the accused was in possession of the dangerous drug; 
(2) such possession is not authorized by law; and (3) the accused freely and consciously possessed the dangerous drug.[17]

Precedents/Link/Source: 
[17] People v. Enriquez , G.R. No. 197550, September 25, 2013, 706 SCRA 337, 349-350.

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[2017V205] PP vs Barte