He gabbed into the wee hours with Houston police detectives about U.S. foreign policy, economics, mathematics - almost anything except the nine slayings he's suspected of committing.
"He would either turn the conversation back to what he wanted to talk about, or he simply would not answer the questions," said Sgt. Tom Ladd.
During a news conference Houston FBI Special Agent Don Clark said that having the suspect in custody gives investigators a good opportunity to identify any "signature" that might be used to connect him with other crimes.
Clark said an example of a serial killer's signature would be Son of Sam David Berkowitz's use of a .44-caliber Magnum.
Resendez, 39, remaines jailed without bond. He is charged with capital murder in the east Texas town of Hughes Springs and murder in Illinois and Kentucky. He could get the death penalty in the Hughes Springs case, the slaying of an 87-year-old woman.
He also is charged with burglarizing the home of a Houston-area doctor killed in December. If Resendez's DNA matches evidence left in her home, Houston prosecutors plan to charge him with capital murder. The FBI is checking on possible links to more than 200 other unsolved killings, though most are expected to produce nothing.
More than 700 requests have been made by law agencies and private citizens to investigate crimes that may be linked to Resendez, Clark said. He said this has been a priority for the admittedly small staff of profilers on the case, and of the over 200 they have been through so far, there have been no new connections.
According to Ladd, Resendez talked extensively about his displeasure with capitalism, the treatment of migrant workers and many U.S. government policies, including the recent air raids in Yugoslavia.
"He does not like America or Americans," Ladd said. "I asked him if he didn't like this country, why was he always here? For that he had no answer, just a blank stare."
The suspect also discussed a mathematical theory concerning the numeral zero, going so far as to sketch a formula.
After he surrendered Tuesday, Resendez agreed to speak to police without an attorney present, but he neither admitted nor denied guilt in any crime, Ladd said. However, he tried to plead guilty during two court appearances on the burglary charge the next morning, saying he wanted to proceed quickly.
Ladd said Resendez's demeanor during the interrogation was the same meek, soft-spoken persona he has shown in the courtroom. He dismissed suggestions that Resendez is not of sound mind or that he was hoodwinked into surrendering with a possible death penalty looming.
"I think his mental capacity is just fine," Ladd said.
Defense attorney Allen Tanner sid Resendez and his family took authorities' promise of "humane treatment" to mean eliminating the chance of capital punishment. There is no death penalty in his native Mexico.
"He and his family understood that he would be treated humanely, and he doesn't think that if they're going to seek the death penalty, that that's humane," Tanner said.
Tanner added that Resendez has not yet sought help from the local consulate, but he hopes they can bring some pressure upon authorities not to seek the death penalty. Thirteen Mexican citizens currently are on death row in Texas.