Question: Is there scientific proof outside of the New Testament accounts that the resurrection is true?
Answer:

While limited in number, there were a few extra-biblical writers who mention Jesus’ resurrection. For example, the Jewish historian Jospehus describes Jesus as… “risen from the dead” three days after being crucified on a Roman cross. The most striking reference though is found in the 5th century Jewish compilation called the Toledoth Jeshu. It clearly acknowledges the “empty tomb of Jesus.” Listen to what Dr. Paul Maier, a bible scholar/researcher, says about the Toledoth Jeshu acknowledgment:
‘”Positive evidence from a hostile source (like this one) is the strongest kind of historical evidence. In essence, if a source admits a fact that is decidedly not in its favor, the fact is genuine.”
I think it would be useful to address the other possible way you may be asking this question. If you mean by “scientific proof,” have a group of scientific investigators tried to determine if the resurrection really happened, apart from the biblical accounts, the answer is ‘no’ and for good reason…
To do that , they would have to either actually have “observed it” themselves or exactly “reproduce it” via a “perfectly controlled” experiment. Obviously, both of these options are impossible – because they would have had to have been there themselves (and we already have explicit accounts from people who were there in Scripture!!) or to “replicate the exact conditions” that occurred during Jesus life, death, burial and resurrection! And, by the way, that would require Jesus Himself to perfectly and completely repeat all of these things to validate the study!!
To truly prove something “scientifically,” you must actually observe, replicate and validate your findings. The “scientific method” is built upon actual “observation” and “reproducibility.”
So, apart from the New Testament record which presents “many convincing proofs” as the beloved physician Luke states in Acts 1:3, there is no other way to understand, examine and prove the resurrection of Jesus Christ (and I believe that was and is God’s perfect plan!!)
The biblical accounts of Christs’ resurrection have been researched extensively throughout the centuries. A number of alternative theories have been offered. However each one completely collapses under the weight of the biblical accounts, when fairly and objectively examined.
Ultimately, those who want to attack the credibility of the biblical accounts of the resurrection are left with one strategy – vigorously try to discredit the truthfulness and reliability of the Bible itself!
But,ultimately, that won’t work either. Isaiah 40:8 puts it this way:
The grass withers and the flower fades but the Word of the Lord stands forever”
For further study on the resurrection of Jesus Christ I recommend the following resources:
Did Jesus Rise From the Dead – Gary Habermas – Tyndale Publishers, 1992.
The Resurrection of Christ: Myth or Reality- Matt Perman (find it at www.monergism.com)