Anngie Gutierrez knows how bodies decompose. She can deduce from a skeleton whether the person who died was a man or a woman. In her high school forensics biology class, she has learned to determine time and cause of death.

The 17-year-old Bladensburg High School junior readily admits her siblings do not share her taste for decomposition: "I am the weird one in the family."

Gutierrez wants to become a medical examiner or a forensic investigator, like the investigators she loves to watch on "CSI." But unlike her two brothers and her sister who were born in the United States, she was born in Guatemala - and is undocumented.

Thousands of high-school and college-age student-immigrants are lobbying Congress, introducing themselves to citizens by scheduling meals together and performing acts of public service to draw attention to the DREAM Act - a measure that seeks to provide legal papers for undocumented immigrants who were brought to the United States when they were children. Gutierrez's parents, who also are undocumented, brought her here when she was 8 years old.

Senate Majority Leader Harry M. Reid (D), who was helped by the Latino vote in his narrow re-election victory in Nevada earlier this month, and current House Speaker Nancy Pelosi (D-Calif.) have said they will advance the measure - technically, the Development, Relief and Education for Alien Minors Act - in the lame-duck session of Congress.

The bill was blocked in the Senate when Reid introduced it before the midterm elections. Advocates and critics both say the odds of it passing in the next Congress are slim, given that a Republican majority in the House is expected to concentrate on immigration enforcement measures. And Republicans have vowed to block the new bill because they believe it would provide amnesty to lawbreakers and legal status to criminals.

While the measure offers a path to legalization for immigrants such as Gutierrez who sign up for two years of college or military service, different versions of the bill currently under consideration would limit the benefit, depending on the age of the person. Military leaders have called for passage of the bill, citing its relevance in preparedness.

Large numbers of Republicans and Democrats once supported the measure, but a shifting tide of public attitudes toward illegal immigration has prompted many Republicans and some Democrats to reconsider.

"Many of these students are my students," Secretary of Education Arne Duncan said at a recent news briefing to champion the DREAM Act. He was referring to students in the Chicago public schools where he worked before joining the administration. "The chance of going to college was denied them. It's absolutely unfair to those children and ultimately unfair to our country."

Duncan said that President Obama was willing to spend "political capital" on making sure the measure passes. Duncan said about 55,000 young people a year could benefit from the DREAM Act.

Opponents cite vastly larger numbers and say the bill would pave the way to legalization for millions of undocumented immigrants and attract new waves of illegal immigration.

Sen. Jeff Sessions (R-Ala.) warned his colleagues in an alert last week that while the DREAM Act could give "green cards" to as many as 2.1 million people immediately, the number could triple within a decade. The measure could offer legalization to people convicted of visa or marriage fraud, or DUI offenses, he said.

The measure calls for students to complete two years of college or serve in the uniformed forces to qualify for conditional permanent residency, but Sessions said that the bar was being set too low. Sessions also warned fellow conservatives that the measure would allow undocumented immigrants to receive in-state tuition benefits.

"When my parents came to the United States, no one asked, 'Do you want to stay or do you want to go?'â" said Jaime Mauricio, 18, of Hyattsville, who recently visited Congress to lobby Republican Sen. Kay Bailey Hutchison of Texas to support the DREAM Act. "I was 9 years old [when his family brought him to America from Honduras.] This is the only country I know."

Gutierrez attended Thanksgiving dinner last week at the home of one of her high school teachers, Elias Vlanton. A group called United We Dream organized 300 to 500 events where DREAM Act-eligible students could share Thanksgiving dinner with citizens - and also perform various acts of service - according to Jose Luis Marantes, a senior organizer at the group.

"All teachers push every day to get our kids to go to college and work hard, and then you have kids who want to do that and are being denied," Vlanton said as he talked about what an exemplary student Gutierrez is. "It's painful - it's painful to you as a teacher."

Gutierrez said she was not sure what she will do if the DREAM Act is not passed.

"I guess they don't see it from our point of view," she said of the measure's opponents. "If the U.S. was an impoverished nation, if Guatemala was the rich country and the one with education, I bet then Americans that are opposing this would say, 'Hey, give us a chance!' But since they have it, they don't realize how important it is to us."