Do Jehovah's Witnesses deny that any crucifixions happened or they only deny crucifixion of Jesus Christ?

WE cannot say in general that no crucifixions never happened however there have been research done on the matter by non-Witnesses. On ABC News July 2, 2010 a Scholar Mr. Russell Goldman had to say "For 2,000 years the crucifix has been a potent symbol of both Jesus Christ's death and Christianity, Now one Swedish theologian says that despite the crucifix's proliferation in art and literature, there is scant evidence in the Bible or other ancient sources to indicate that Christ was killed on a cross." Gunnar Samuelsson, an evangelical preacher and theologian, says he spent three years combing thousands of ancient texts to research in his recently completed 400-page doctoral thesis "Crucifixion in Antiquity." What he discovered, he said, came as a shock. While there were numerous references to "suspension devices" used for executions at the time of Christ death, HE COULD FIND NO EXPLICIT REFERENCES TO THE T-SHAPED CROSS. "There is no distinct punishment called `crucifix' anywhere mention in any of the ancient text including the Gospels," he told ABCNews.com. Samuelsson devoutly believes the story of Jesus' death and resurrection, but says FOR GENERATIONS PEOPLE HAVE MISINTERPRETED AND MISTRANSLATED THE GREEK WORD "STAUROS" TO MEAN CRUCIFIX, WHEN REALLY THE TERM JUST MEANS A SUSPENSION DEVICE, WHICH MIGHT HAVE BEEN ANYTHING SUCH AS A "POLE OR A TREE TRUNK." the earliest versions of the New Testament were written in Greek. "If you chose to just read the text and ignore the art and theology, there is quite a small amount of information about the crucifixion. Jesus, the Bible says, carried something called a STAUROS out to Calvary. Everyone thought it meant cross, but it does not only mean cross. We cannot say every instance of this noun, STAUROS refers to a cross," Samuelsson said. SUSPENSION DEVICES, BASICALLY TALL POLLS OR PIKES, WERE ROUTINELY USED IN THE ANCIENT WORLD, BY THE ROMANS AND THEIR CONTEMPORARIES, BOTH AS EXECUTION DEVICES AND FOR DISPLAYING THE BODIES OF EXECUTED CRIMINALS and enemies as a public warning. Part of what tipped Samuelsson off to the apparent mistranslation, were routine references to things like fruits and dead animals being "crucified" in ancient text, when translating the word as "suspended" makes more sense.Evidence is, therefore, completely lacking that Jesus Christ was crucified on two pieces of timber placed at right angles. We do not want to add anything to God’s written Word by inserting the pagan cross-concept into the inspired Scriptures, but render stau·ros′ and xy′lon according to the simplest meanings. Since Jesus used stau·ros′ to represent the suffering and shame or torture of his followers (Mt 16:24), we have translated stau·ros′ as “torture stake,” to distinguish it from xy′lon.