http://truthvoice.com/2015/07/san-diego-defense-attorney-explains-10-ways-cops-are-allowed-to-lie/
“An informative essay titled 10 Ways the Police Can Lie to You appeared on the website of San Diego criminal defense attorney Nicholas J. Moore. The essay details a number of deceits and tricks investigators may attempt to get a confession — true or otherwise — out of a suspect.

From the essay:

As a general proposition, police are allowed to lie. The lies told by the police to a suspect under questioning do not render the confession involuntary per se. Mere trickery alone does not invalidate a confession. The court must look to see whether the deception is reasonably likely to produce a false confession. People v. Farnam (2002) 28 Cal.4th 107;Hawkins v. Lynaugh (5th Cir. 1988) 844 F.2d 1132”