Mementos and notes covered American University accounting professor Sue Marcum’s office door Oct. 26, the day after her body was found. (Gerald Martineau/FOR THE WASHINGTON POST)

DNA found on a weapon suspected in the killing of American University professor Sue Marcum connects fugitive Jorge Landeros to her death, according to an FBI affidavit filed in federal court.

The affidavit, filed as part of a complaint charging Landeros, 41, with unlawful flight, also offers a possible motive in Marcum’s death. It alleges that Landeros was on the move in the days before the killing, crossing from his native Juarez, Mexico, into the United States.

Marcum, 52, a popular accounting professor, met Lan­deros about six years ago when he lived in the Washington area. In 2008, “she made the initial contribution” to an investment fund that the two were “jointly involved in,” according to the FBI. Proceeds from the fund appeared on a 2008 IRS Form 1099 in Marcum’s name, the affidavit says.

“In recent electronic mail between Marcum and Landeros,” the affidavit says, “it was clear that Marcum, a university professor who may have had an intimate relationship with Landeros, was increasingly uncomfortable with the fashion in which Landeros was handling and spending the account funds.”

It is the first time authorities have linked a possible dispute over money to Marcum’s death.

Authorities for the first time have linked a possible dispute over money to accounting professor Sue Marcum’s death. (Courtesy of American University)

Marcum’s body was found in her Bethesda house Oct. 25. The case initially looked like a burglary that had gone bad.

But Montgomery County detectives slowly built a case against Landeros, a poet and yoga instructor, obtaining a first-degree murder warrant April 16. Since then, they have tried to lure Landeros out of Mexico, where he has taken to taunting them in e-mails saying that he wasn’t willing to travel to the United States but that he wasn’t hiding out, either. Last month, Landeros was teaching yoga three days a week at a cafe in Juarez, a posting openly promoted on the Internet, according to the affidavit.

In interviews with The Washington Post this month, Landeros said his DNA would be found in Marcum’s home because he had spent so much time there. He said he was in Juarez in late October when Marcum was killed.

“I had nothing to do with the murder of Sue Marcum,” Lan­deros said. “That was not me.”

Landeros could not be reached for comment Sunday. He said two weeks ago in his last interview with The Post that he would not speak again about the case.

Landeros’s attorney, William Brennan of Greenbelt, declined to comment on the affidavit.

The FBI affidavit, filed this month in U.S. District Court in Greenbelt, does not specify what kind of weapon police think was used in the crime.

Jorge Landerosis sought in thekilling of Sue Marcum. (INTERPOL)

Capt. Paul Starks, a Montgomery police spokesman, said detectives are working with national and international agents to try to track down Landeros. He declined to comment on the affidavit.

The affidavit listed the proceeds from the investment fund at $100 million, but that figure almost assuredly was not profit. At the time, Landeros was actively day-trading stocks. What is unclear is how much he spent buying stocks during that time and how the total compared with his stock sales.

Marcum studied accounting and received a master’s degree in taxation in 1987 from American. She later joined the school’s faculty. Outside class, she pursued a variety of interests, including learning Spanish, and she met Landeros in about 2005 when she enrolled in one of his Spanish classes in Dupont Circle.

Landeros was born in Juarez, spent part of his youth in Ohio, traveled through Europe, wrote poetry and worked as a stockbroker. After meeting Marcum, he was soon going by her home in the mornings to practice yoga and meditation. She eventually made him the sole beneficiary of a $500,000 life insurance policy, according to Landeros and the FBI affidavit.

In 2008, Landeros and his friends said, he left the Washington area to return to Juarez. Landeros said he last saw Marcum in September, when he traveled to Northern Virginia to visit his mother. He said he was back in Juarez when Marcum was killed.

But according to the FBI affidavit, U.S. Border Patrol records showed that Landeros crossed from Juarez into the United States on Oct. 21, four days before Marcum was found dead.

Although the FBI affidavit implies that Landeros could have traveled to see Marcum at the time, Landeros’s father lives in El Paso, and until recently Landeros regularly crossed the U.S.-Mexican border to visit him. Landeros has dual citizenship and could cross the border with ease, police said.

As Montgomery detectives became more convinced that Lan­deros was their suspect, they enlisted detectives in El Paso to obtain a DNA sample from him on one of his trips to the United States. On April 15, according to the FBI, Montgomery forensic investigators matched Landeros’s DNA with evidence lifted from the weapon found in Marcum’s house.

The next day, authorities obtained a warrant charging him with first-degree murder. By that time, Landeros was back in Mexico.

Federal authorities say that Landeros is well aware that he is wanted in Marcum’s killing but that he has declined to turn himself in.

Friends of Marcum’s said Sunday they did not know about the investment fund, and that a lot of things about her relationship with Landeros don’t seem to make sense.

“This is the Sue that we did not know,” said Cathy Vincent-Smith, a close friend.