I remember watching this horror flick about 6 years ago on some local tv channel. It was in English (American), in color, and it was probably made in the 2000s or maybe 2010. The plot was about a group of people trapped in a prison-like place with a green alien. The alien could imitate the voice and appearance of everyone it killed. It had green blood and diamond was its only weakness. The movie starts with a lady with red hair recalling the incidents and talking about them to police officers in the same prison. Then it turns out that the lady is actually the alien and it kills one of the officers. The other officer is the one who finds out about its weakness and tries to defeat it. Another scene shows the surviving officer doing the same thing the red-haired lady did, talking to some officers about what he remembers. Turns out this is the alien speaking again, not the actual officer. Also the alien laid eggs. I vaguely remember the title of the movie starting with “R”. Something like “Reptilian” maybe? However I cannot find the movie with this name, so maybe I’m wrong.

Sounds quite cheesy, but help is appreciated.