Last April when the FBI finally caught up with the young Polish gypsy named Christina, they found her hiding in a closet in a house full of gypsies in Brooklyn, N.Y.

It appeared to be the end of a two-year odyssey around the country for Christina, during which the government contends she used four different aliases, was arrested five times on various offenses and convicted once - all the while wanted in the District of Columbia on burglary charges.

Prosecutors who might have thought that her straighforward case would be swiftly closed in court have found Christina just as elusive in the courtroom: her trial has been postponed for months because no one has been able to determine exactly her age.

The point is a crucial one, for if she is found to an adult, she faces a lengthy prison term if she is convicted. As a juvenile, conviction would most likely result in a much less severe penalty.

Christina claims she was a juvenile, not an adult, when she was arrested on the burglary charges in the District of Columbia in 1975. She thus protested through her New York attorney after her arrest in April that she could not be extradited to Washington to answer charges.

She has no birth certificate to verify her age, which she says is now 17, but relies instead on some immigration papers - which the government says are based on false information - and the testimony of a man who claims to be her father, plus that of a cousin who claims to be the "king of gypsies" in Chicago and an eyewitness to her birth in Poland.

At a hearing before Judge H. Carl Moultrie in D.C. Superior Court last summer, Christina's father also testified that his daughter has adhered to a "gypsy custom" that women must remain virgins until they are 18 years old.

To prove that point, Christina's Washington attorney, former Superior Court Judge Harry T. Alexander, had his client examined by gynecologist who testified that, in his opinion Christina is a virgin.

In court papers, the government called that testimony "absolutely meaningless." Instead, the U.S. Attorney's office produced a dentist, certified as an expert in determining age through teeth, and a radiologist who examined Christina's bone structure to estimate her "skeletal age." Their combined estimates put Christina's age somewhere between 17 and 20 according to court records on her case.

Judge Moultrie apparently not convinced by the counter-testimony of another dentist and radiologist for the defense who said Christina was 17, ruled that she was over 16 at the time of the alleged burglary here and thus could be tried in adult court as the government intended.

Alexander took the issue to the D.C. of Appeals, where the question of Christina's age was argued before a three-judge panel last month. In the meantime, the ageless Polish gypsy sits in the Women's Detention Center on North Capitol Street, where she is being held on a $75,000 bond.

When she was returned to Washington last April, the government argued for the high money bond for Christina because they alleged that twice she failed to show up for court hearings on the burglary charges. As a result, she has been charged with violations of the D.C. Bail Reform Act.

In papers filed in the D.C. Superior Court, the U.S. Attorney's office claimed that Christina is acquainted with a Newark, N.J., man who is known to police officials there as a gypsy "bail man" who travels from state to state "for the purpose of posting high money bonds for gypsies who have been arrested."

Christina's odyssey began in April 1975, when she was first arrested on the burglary charges in Washington. She was released after posting a $500 bond - and then failed twice to show up for hearings in Superior Court, according to records of her case.

In June she was arrested in Milwaukee and convicted of criminal trespass but released before authorities there discovered she was wanted on a warrant from the District of Columbia, the records said.

The following September, Christina was arrested in Chicago on burglary charges, all of which were later dismissed, the records said. In December, she was charged with theft, also in Chicago, but the disposition of that case is unknown, according to records here.

In January, 1976, when Christina heard that FBI was looking for her connection with the Washington charges, she surrendered in D.C. Superior Court, the records revealed. Christina again was released on bond and returned to Chicago, where she was arrested in February for theft but no formal charges were filed, the records showed.

A trial date was set for March, 1976, on the Washington charges and Christina attended that hearing. But the trial was then postponed until June, the records show, and subsequently she failed to appear in a court. In October, 1976, records reveal, she was arrested in Frackville, Pa., on burglary charges along with several other gypsies. But those charges were dropped after an "associate" of the group paid $8,000 to the victims, the record showed.