Were the witnesses to Christs resurrection martyred?
The answers is yes, some of them definitely were martyred, and most likely a significant proportion of the original witnesses of the resurrection were killed for their faith. There are two categories here. One, there are the original eyewitnesses about whom we can be virtually certain they were martyred for their faith. These include both the apostle James and James, the brother of Jesus. Josephus, the Jewish (but not Christian) historian reported both of their deaths, and they certainly were among the eye witnesses. Then there is Stephen, who certainly was martyred but who may or may not have been one of the eye-witnesses. Also, there is Peter whose martyrdom was not reported by a contemporary but who many early Christians reported to have been killed in Rome. Virtually all scholars will agree that Peter was killed for his faith. Then there are others such as nearly all the apostles whose martyrdoms are reported by Eusebius. Eusebius is generally a reliable historian, but he wrote in the early 4th century, so his witness is somewhat uncertain. Also there is Paul. He claimed to be an eye-witness and he certainly was martyred.
So, we can say absolutely for sure that a few of the eye-witnesses were martyred, that almost certainly more than a dozen of the witnesses were martyred, and it is very possible that several dozen of them were. The fact is that we neither know the names nor the ultimate fates of most of these men and women. The truly amazing fact is that, as far as we know, not a single one of these brave men and women every repudiated their claim that they witnessed Jesus alive after his death on a cross. This is powerful evidence that Jesus did in fact raise from the dead on the third day.