The president of the National Autonomous University of Honduras, Julieta Castellanos, spoke out Wednesday against what she says is police sabotage of the investigation into the murder of her son and another student.

"There has been a process of tampering with evidence, there has been a process of obstructing the investigation. The police have engaged in double-talk," she said during a protest outside congress to demand an overhaul of the country's police force.

While police say they want to capture those responsible for the crime, "on the other side they intimidate the prosecutors, the investigators and the medical examiners," Castellanos told hundreds of college students in Tegucigalpa.

Her son, Rafael Vargas Castellanos, and friend Carlos Pineda were killed in the wee hours of Oct. 22 while driving home from a party.

The 22-year-old Vargas Castellanos was studying law and the 24-year-old Pineda was finishing a degree in sociology.

Investigators quickly focused on police officers as the likely killers, but though four of the suspects are in custody, four other cops implicated in the crime were allowed to remain at large and are now fugitives.

Julieta Castellanos stressed, however, that Wednesday's protest was about more than one case.

Knowing how her son and his friend died and seeing the killers held accountable is not enough, she said, insisting on the need for a "profound cleansing of the police."

The slayings of the students has rocked this Central American nation, which, according to a recent U.N. report, leads the region with a rate of 82 murders per 100,000 residents.

President Porfirio Lobo responded to the outcry by announcing a shakeup of the police high command, but critics said the move amounted to no more than "rotations" of officers between posts.

Wednesday's edition of capital daily La Tribuna included a letter purporting to be from veteran police officers who urge Lobo to fire some of the commanders named to new positions in the personnel shuffle.

"We request an exhaustive and decisive investigation of three of the recently named directors, because there are and have been strong indications that they have been linked to organized crime and, more specifically, to drug trafficking and murder-for-hire (this is public knowledge inside the National Police)," the letter says.

Julieta Castellanos was a member of the truth and reconciliation commission that issued a report earlier this year on the events surrounding the June 28, 2009, coup that ousted President Mel Zelaya.

She also founded a watchdog organization that has exposed official abuses and corruption.

Lobo, who was elected in November 2009 in a process marred by violence, media censorship and low turnout, has so far failed on his promise to improve public safety.

Few murders are ever solved and Honduran authorities routinely ascribe violent acts to "score-settling" within and among the country's youth gangs and criminal outfits.

At the same time, many of the killings since Zelaya's ouster appear to be politically motivated, as victims are often associated with the resistance movement that sprang up in the wake of the coup.

The deposed head of state returned to Honduras five months ago under a pact brokered by regional leaders, but violence against his supporters and other activists continues.