He nearly certainly had no idea that lab technicians had linked DNA on two pipe bomb packages he was accused of sending to prominent Democrats to a sample previously collected by Florida state authorities.
Authorities say Sayoc faces more than 50 years in prison if convicted on all charges.
The Brooklyn-born Cesar Sayoc, 56, is charged with five felony counts - interstate transportation and illegal mailing of explosives, threatening a former president, making threatening interstate communications and assaulting federal officers.
The defendant, wearing a khaki prison jump suit, shackled and surrounded by US marshals, said nothing during the brief hearing but seemed to be fighting back tears.
Sayoc spoke little during the brief hearing.
Sayoc, his salt-and-pepper hair pulled back into a ponytail, remained largely silent, only acknowledging Judge Edwin Torres'reading of the charges against him.
Attorney Daniel Aaronson conceded after court that the case will be moved to NY but that Sayoc is entitled to a hearing in Miami to see if he will get bail while awaiting trial.
Trump has said he should not bear any responsibility for the heated political rhetoric apparently harnessed by Sayoc.
One of Sayoc's attorneys, Daniel Aaronson, urged people not to rush to judgment based on media reports. Sayoc eventually clammed up, invoking his Miranda rights and asking to speak with a lawyer. It was a stark contrast to the man accused of a campaign of fear that continued on Monday as another suspicious package was intercepted Monday in Atlanta, addressed to CNN headquarters. None of the devices detonated, and no one was injured.
Lopetegui hopes to save Madrid's season_ and job_ at Barca
So it is quite obvious that with or without one of the world's greatest players, the club will continue to push for all trophies. " Real Madrid is still alive".
On Friday, Sayoc, a Florida resident working most recently as a strip-club DJ, was arrested, suspected of mailing pipe bombs to prominent Democratic politicians and donors, including former President Barack Obama, former Secretary of State Hillary Clinton and philanthropist George Soros.
Authorities did not immediately say who might be responsible for sending the most recent package, but law enforcement officials have said they believe the packages were staggered and more could be discovered.
- Donald J. Trump (@realDonaldTrump)There is great anger in our Country caused in part by inaccurate, and even fraudulent, reporting of the news.
Sayoc told investigators after he was arrested in Plantation, Florida that the pipe bombs wouldn't have hurt anyone, and that he didn't want to hurt anyone, according to a law enforcement official.
At Monday's hearing, federal prosecutors said they will seek to keep Sayoc jailed until trial as a flight risk and a danger to the community.
A sketch artist captures package bomb suspect Cesar Sayoc's first appearance in a Miami federal courtroom.
In a press conference Friday, FBI Director Christopher Wray said the suspicious packages recovered by authorities were "not hoax devices" and warned of other packages that could surface, saying the investigation's progress so far "does not mean we're out of the woods".
The bombs were sent in manila envelopes lined with bubble wrap and consisted of plastic 6-inch pipes packed with explosive material and wired to small clocks and batteries, a criminal complaint filed in Manhattan federal court said.
The video shows Sayoc casually chatting with co-workers, eating and rifling through stacks of papers.