"There's nothing I believe in more than jahar's innocence," tweeted an 18-year-old from Kansas with the handle @keepitbluntedd, using the popular hashtag #freejahar, a reference to the suspect's nickname.
Surveillance videos near the finish line of the Boston Marathon April 15 show two men who authorities believe to be Dzhokhar and his older brother, Tamerlan Tsarnaev, placing backpacks on the ground thought to contain pressure cookers filled with explosives and shrapnel minutes before the twin explosions.
Three people were killed and more than 260 others injured, many of them critically.
Tamerlan Tsarnaev, 26, was killed during a shootout with police April 19.
Dzhokhar was captured hours later and quickly became an internet phenomenon. He is being held at a federal medical detention centre in Devens, Massachusetts, charged with using a weapon of mass destruction.
"If they did do it I strongly believe jahar was dragged into it. Im Not saying that thats OK just saying it wasn't his idea," wrote @nicole82211.
A YouTube video entitled "Things you don't know about Dzhokhar" showed the suspect before the bombings doing such normal American teen things - goofing off with his friends, wondering about girls, dreaming of pizza - so scores of teens who might have seen the video in the US might relate to him and feel sympathy.
Frustrated with the media attention to the growing online support for Dzhokhar, 14-year-old Bethany Brown posted a message to reporters: "Ok!! Media shut the hell up!! We are supporting him! We are not here because he's cute!!"
She told RIA Novosti in an email exchange that she thought Dzhokhar was cute, but insisted that had nothing to do with her views about the case.
"I do believe 99.9 percent that Jahar is innocent," she wrote.
"My parents think he's guilty and think I'm crazy for supporting him."
"What if Jahar started crying during the trial? I know I would," gushed @jtsarisinnocent.
"This is about juvenile fantasy, and nothing more," said forensic psychiatrist Dr. Park Dietz, an expert witness in a number of high-profile criminal cases in the US, in an interview with RIA Novosti.
The same thing has happened before with high-profile, infamous American killers including Ted Bundy, Richard Ramirez and Timothy McVeigh, Dietz said.
The likelihood of a suspected killer becoming the subject of such attention "depends on two things: how famous is he and how cute is he... so if he's famous and cute enough, he can attract lots of fantasy", he said.
"Jahar is kind hearted. he is innocent. he is pure," said a message posted on Twitter by the anonymous Twitter handle @freejaharlove, which later posted, "jahar is innocent spread the message".
The site also posted a link to a YouTube video in which controversial talk show host Alex Jones claims Dzhokhar was tortured into confessing.
"Never gonna get a fair trial, folks, never gonna get a fair trial," Jones said.
But, in case Dzhokhar is found innocent, an anonymous posting on the social media site PasteBin includes a romantic fantasy about what might happen on the day he is freed.
"... there stood Jahar in front of me with a large smile gracing his face. With two large steps he closed the distance between us and pulled me into his chest, holding me tightly."
Those who are expecting the kind of scene in which the music plays and the screen fades to black might be disappointed to learn that the writer imagines the two of them eating pizza and watching "Lord of the Rings", all the while mumbling sweet nothings to each other.
On Facebook, the Dzhokhar Tsarnaev Free Jahar movement has more than 6,600 members.
"Dzhokhar Tsarnaev, a young man of 19 years of age's life has been stolen and has been made into a public object of hate, created by the inaccurate reports by the media. We believe in innocent until proven guilty by undeniable evidence, which so far has not been provided," said the group's profile page.
"This can happen to you or any of your children," it added.
@keepitbluntedd posted plans to get one of Tsarnaev's tweets tattooed on her arm: "If you have the knowledge and the inspiration all that's left is to take action", but later announced she was delaying those plans "out of respect of my family's wishes".
It was not all cheers of support for the suspected Boston bomber.
Messages using the #freejahar and other similar hashtags have been hard hit with a visceral, scathing public reaction. Several made graphic suggestions about prison life for the baby-faced suspect.