For the fourth time in four weeks, a Montgomery County court yesterday acquitted a defendant of sexual offenses against a child.

Circuit Court Judge Irma Raker found innocent a cabdriver accused by a Potomac family of molesting their 3-year-old daughter last fall when he was driving the child home from nursery school.

Raker acquitted Emmanual Cazeau, of Silver Spring, of a third-degree sexual offense.

Raker also dismissed a charge of child abuse against Cazeau, saying the state had not proven that the cabdriver had temporary or permanent care or custody of the child, required under Maryland's child abuse statute.

The acquittal comes at a time when child molestation cases have become almost routine in courts across the nation. It also underscores the difficulties inherent in children testifying in such cases or refusing to testify.

"We are going to trial with cases which before we disposed of by alerting family and friends and putting the parties into therapy," Montgomery County State's Attorney Andrew L. Sonner said in a telephone interview after the acquittal. "The conventional wisdom today is that these cases need to be tried -- that that's the therapy. And the large number of acquittals is not a surprising outcome.

"Almost by definition, they are cases with weaker evidence than we usually go to trial with," Sonner said. "In an armed robbery case, we usually don't have 3- or 4-year-old witnesses. In this type of case the defendant picks the victim and we can't find experienced witnesses."

In yesterday's case, the girl, now 4, refused to take the witness stand. But her grandmother testified that she was upset when Cazeau dropped her off last Sept. 18 and, under questioning, said the man had molested her, according to the grandmother's testimony.

Cazeau, 35, a cabdriver for Barwood Cab Co., testified in his own defense that he had never bothered the girl.

In the three other child molestation charge acquittals in the past month:

* Circuit Judge William Miller acquitted a government meteorologist March 21 of charges he molested his adopted daughters, ages 9 and 5.

* A county jury March 22 found a Silver Spring church deacon innocent of charges he molested a 7-year-old Howard County girl at the church. The man still faces similar charges in two other cases.

* A Gaithersburg executive was acquitted by jury April 9 of charges that he sexually abused his 4 1/2-year-old granddaughter.