A Phoenix mother admitted to killing her 6-day-old baby girl because she "had too many kids already," police say.

According to court documents obtained by New Times, the woman, 36-year-old Nina Koistinen, has prior run-ins with Child Protective Services and previously had said she wanted her children "to go to heaven in a vehicle accident that appeared intentional."

According to police, Koistinen's husband found his 6-day-old daughter, Maya, unresponsive inside their home, near 56th Street and Thunderbird Road, on the morning of April 8.

Maya was pronounced dead that morning at a hospital.

According to court documents, "possible signs of suffocation" were discovered during an autopsy, and police dug up the CPS records on Koistinen.

In addition to her comment about killing her kids in a car crash, she also talked about "wanting to smother some of her children," according to the documents.

Police didn't arrest Koistinen after her initial interview with police but did after her second interview, conducted Thursday at Phoenix PD headquarters.

"During the interview, Nina admitted she smothered Maya because she thought she had too many kids already and she was jealous of the attention [her husband] was giving baby Maya," a probable-cause statement says. "The father . . . was put in the interview room with Nina and she admitted to him that she pinched Maya's nose, twisted, suffocated, and smothered baby Maya."

Koistinen was booked into jail on one count of first-degree murder.

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