Help -- Interpreting EZ test reaction?

Dunno if anyone can help....friend tested some pills (plain white mitsi- no specks, Perth, well pressed, thick), went very dark brown straight away....sitting for a minute or so and finished up black?
Pretty new to the EZ test colour changes so I am not sure, didn't know what to tell friend...sounds like speed, but usually that is orange first then brown isn't it? Also this went extremely dark brown, darker than on the chart supplied.
Any suggestions?

forgot to add..pill has NO split..

yes they are a dodgy pill
looked at a few bought one
not game to try it its not pressed well lookes like and tastes like speed hence looked elswhere. will use as aditive to smacky pill if nessacery look forward to others reply to your question

perth