The presumption of regularity in the performance of duties of public officers can be overturned by what?

Courts are cognizant of the presumption of regularity in the performance of duties of public officers. This presumption can be overturned if evidence is presented to prove either of two things, namely: 

(1) that they were not properly performing their duty, or 

(2) that they were inspired by any improper motive.[15] 

Precedents/Link/Source: 
[15] People v. Remarata, G.R. No. 147230, April 29, 2003, 401 SCRA 753, 754.

2017 Latest Application. READ Full Text.
[2017V205] PP vs Barte