Sources close to Amber say Johnny has a relationship with LAPD cops ... they say some have worked off-duty in his security detail.
We're told Amber is adamant ... she had obvious facial injuries when cops responded to the 911 call on May 21, and there is no reason for them to deny it other than to protect Johnny.
Amber says a witness was present when cops responded. Her name is Raquel Rose Pennington, and Amber says Raquel examined her face which she says had "a significant injury with redness and swelling."
Our Amber sources also note the LAPD has changed its story multiple times ... first telling the media they never responded to a 911 call involving Amber and Johnny, then saying there was only one call, and later admitting they received 2 calls and sent 2 different sets of officers to her apartment.