An Arizona woman has been arrested for allegedly trying to kill her estranged husband by poisoning his daily coffee for months - while he used hidden cameras to catch her in the act. Melody Felicano Johnson was indicted by a Tucson grand jury on charges of first-degree attempted murder (domestic violence), attempting to commit aggravated assault (domestic violence) and poisoning food or drink, according to court documents obtained by KVOA. She pleaded not guilty at an arraignment on Friday. Prosecutors say the plot to poison her husband Roby Johnson, a member of the US Air Force, began back in March when he noticed a strange smell in his coffee. The couple, who share a child and were living together while going through a divorce, were stationed in Germany at the time. A few weeks later, Roby Johnson investigated his suspicions with pool testing strips, which showed high levels of chlorine in the coffee pot, the indictment states. In May, he placed hidden cameras that allegedly captured Melody Johnson pouring something into the coffee maker. Roby Johnson reportedly told investigators that he pretended to drink the coffee until the couple returned in June to the US, where he was stationed at Davis Monthan Air Force Base. He then set up multiple hidden cameras again to catch her in the act. The footage showed Melody Johnson “take bleach, pour it into a container and then walk over and pour it into the coffee maker”, the indictment states. An official investigation was launched after Roby Johnson turned the footage over to police as he filed a report. He told investigators he believed Melody Johnson wanted to kill him to collect his death benefits. Melody Johnson is currently being held in the Pima County Jail on $250,000 bond after prosecutors convinced a judge she poses a flight risk, having recently purchased a house in the Philippines near her family. Her next court appearance is scheduled for 6 September.