DENVER -- A Denver woman is being frightened by hand-delivered letters left at her home, supposedly sent by a man who's in prison, police said.

The 29-year-old woman received two letters left in the front yard of her Kalamath Street home with the sender identified as an inmate serving time in Colorado prison for felony assault and menacing, according to court records.

The man also has prior convictions for stalking, assault with a deadly weapon and violating a restraining order in a domestic violence case, court records state.

TheDenverChannel.com is not identifying the inmate because he has not been charged in the harassment case.

The woman said she's disturbed by the letters because the writer referred to her by name and noted that she was a dental assistant who was "off-duty," according a Denver police detective's search warrant to obtain the prison inmate's DNA.

Police hope to match the saliva from whoever licked and sealed the envelopes to the suspect.

But if the imprisoned suspect cannot hand-deliver the letters to the woman's yard, who is dropping them off?

"Denver police are trying to determine how the letters got into her yard at this point," said police spokesman Sonny Jackson. The woman has also received mailed letters from the inmate.

Jackson said investigators have spoken with the suspect in prison and obtained the court-ordered DNA cheek-swab sample from him. But he declined to comment further to avoid compromising the ongoing investigation.

The woman told police she is alarmed by the rambling letters, which appear to be from an invisible stalker. The writer knows details about her and her family members and their physical descriptions, although the woman said some of the letter information is clearly wrong, according to the search warrant affidavit.

The woman said she's never heard the inmate's name and she didn't recognize a photo of the man that police showed her.

"You Father told me he's been here for 44 years," the writer said in the typo-riddled letter found in the yard in mid-November. "[The father] said he [has] four … daughters, including one who was born in 1978 who always has just only wavy, Fluffy soft, wavy hair, another one … fourth-daughter, born in 1981, that always -- has straight sleek hair, always wearing, always wearing sunglasses."

The letter states that the woman's father said that a neighbor the writer described as "mr. ERIC … is only but a neighbor/and Nothing else," according to the search warrant affidavit.

It's not clear whether the woman's father ever spoke to the suspect.

The father found the November letter in the front yard and his daughter contacted police immediately, the affidavit said. The woman also gave police another letter left in the yard Dec. 8, on which police crime laboratory technicians found the presence of saliva and skin-cell material that was processed for DNA.

At least one of the letters identified the sender by the inmate's name and inmate number with a return address for the Department of Correction's Denver Reception Diagnostic Center. The maximum-security facility is where all incoming DOC inmates are processed, tested and classified before they're assigned to a prison.

The inmate was in Denver jail from March 17, 2009 until Oct. 6, 2009, when he was sent to the prison reception center, said DOC spokeswoman Katherine Sanguinetti. On Dec. 4, he was sent to San Carlos Correctional Facility.

"If he is sending (the hand-delivered letters), it seems as if he has an accomplice," Sanguinetti said.