An Arizona woman is accused of attempting to kill her husband by poisoning his coffee every day for months.

Melody Felicano Johnson of Tucson was indicted by a grand jury on charges of first-degree attempted murder, attempting to commit aggravated assault and poisoning food or drink.

Court documents obtained by CNN affiliate KVOA state the suspect's husband, Roby Johnson, began noticing a foul taste to his coffee back in March while he and Melody Johnson were stationed in Germany.

Roby Johnson is serving in the US Air Force, according to police. The statement of probable cause says the Johnsons were still living together with their child but were going through a divorce.

Roby Johnson used pool testing strips to discover his coffee pot "showed high levels of chlorine," the court document says.

He allegedly used a hidden camera to discover Melody Johnson pouring an unknown substance into the coffee maker.

Johnson told investigators he pretended to continue drinking the coffee so he could wait until they returned stateside to Davis Monthan Air Force Base before filing a police report.

Back in the US, Roby Johnson said he used multiple hidden cameras over several days "showing Melody take bleach, pour it into a container and then walk over and pour it into the coffee maker." Investigators say Roby Johnson "believes she was trying to kill him to collect death benefits."

Melody Johnson entered a not guilty plea at an arraignment Friday.

She was assigned a public defender, who did not immediately return a request for comment from CNN Saturday. She is being held at the Pima County Jail pending her next scheduled court appearance on September 6.

Court records show bond for Johnson set at $250,000. Prosecutors told the judge a high bond was necessary because the suspect recently bought a house in the Philippines near family and is considered a flight risk.