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Screen shot of the "Serial" website, teasing episode seven. Serialpodcast

Episode 7 of "Serial," the popular weekly audio podcast that unpacks an actual murder case of a high school girl, features an expert from the Innocence Project who evaluates the case against Adnan Sayed, the son of Muslim immigrants, who was convicted of murdering his ex-girlfriend in 1999. The show's host, Sarah Koenig, also learns about another murder case that resembles Adnan's.

In that other murder case, Koenig discovers that seemingly damning cell phone tower records helped convict Jason Wolf of murdering a drug dealer, much as prosecutors used cell phone tower records in Adnan's case. Wolf was convicted after the shooter, Owen Barber, said Wolf hired him to kill the dealer and accepted a plea deal to avoid the death sentence. Prosecutors used Barber's testimony to get Wolf sentenced to death.

In the case against Wolf, the prosecutors used calls placed before and after the murder as proof of Wolf's guilt. That looked pretty bad for Wolf until other exculpatory phone records from the same timeframe were introduced into evidence. Those phone records helped overturn Wolf's conviction.

The tendency of the same set of phone records to look damning to some people (such as jurors) but vindicating to others (Adnan's supporters) is highlighted by Adnan in an earlier interview with Koenig. Adnan uses a graph about the hypothetical price of tea. In Adnan's hand-drawn graph, he shows the changing price of tea in stores but uses different measurements. In the first graph, Adnan uses increments of $0.40, while the the second graph is in increments of $0.05. If we narrow in our focus, price fluctuations look more extreme even though they are the same between the two stores. It's just a matter of perspective, argues Adnan.

Koenig brings in Deirdre Enright from the Innocence Project to look over Adnan's case. Enright dives in and quickly notes how little evidence there was against Adnan. Enright has her doubts, and she eases Koenig's mind by confirming that wild oscillation when weighing guilt vs. innocence is common.

Enright begins to look at the case against Adnan, and with the help of two members of her team, Katie and Mario, and it becomes clear there are a lot of unanswered questions. The lawyer shows an email that says some evidence may have been destroyed and the team highlights some of the same problems Koenig has addressed -- such as Jay's inconsistent story and the cell tower records. The team adds even more doubt by looking at the lack of forensic evidence in the case. The liquor bottle, two fiber samples and rope found near Hae's body were never tested for DNA. A swab test as part of the Physical Evidence Recovery Kit, or PERK, was tested only for semen, not DNA.

Enright, Katie and Mario all question Adnan's guilt and, based on the evidence, they believe he would be just a person of interest at the moment -- not the actual perpetrator. However, there's just enough there to take the case to trial, says Enright. With that in mind, Koenig once again turns her attention to "Jay," a former friend of Adnan, who testified against Adnan. Jay's actions fit a few of the criteria laid out by Enright, including a possible motive and an easy plea deal for Adnan's conviction. For more "Serial," check out our episodes 1-6 recap and timeline.

"Next time, on 'Serial.'"