Leading up to Parshas Shlach Lecha, the Jewish Content Network held a debate on Murex trunculus as the source of techeles. The first 20 minutes is also fascinating, but it's on a very different subject, the question of Palestinian Authority payments to terrorist murderers, so you may want to skip that.

In support of Murex trunculus is Rabbi Yisroel Barkin, a nephew of Rabbi Belsky zt"l and an expert on techeles. Arguing against Murex trunculus is Rabbi Dovid Bleich, who heads the Bnei Yehuda congregation on the West Side and one of the rosh yeshivas at Yeshiva University.

Rabbi Barkin brings a list of strong proofs from the Gemara. Rabbi Bleich counters by relying on a well-known argument from the Beis HaLevy that whether or not you have solid proofs, techeles requires a masora handed down from generation to generation. He compares it to identifying kosher birds.

Finally, Rabbi Nachum Eisenstein, the rabbi of Jerusalem's Maalot Dafna neighborhood, said that the leading charedi rabbis instructed people not to adopt it, and then reiterates the Beis HaLevy's approach. He says that the leading poskim had all the relevant information presented to them, but did not offer their support. This was hard for me to understand, because I know that Rabbi Eliashiv specifically chose not to examine the issue. Also, one of his leading talmidim, Rabbi Moshe Karp, eventually was persuaded in favor.

You could say it wasn't such a fair debate because the host is a strong proponent of Murex trunculus.