There is no evidence that Jay could have killed Hae so quickly and easily given that they are not known to be close friends.

What was Jay's motive to kill Hae?

To support their case, the prosecution relied on Jay's testimony and on AT&T records of which cell phone towers pinged when Adnan phone received a call. They claimed Adnan's motive for killing Hae was he was angry with her for breaking up with him and was jealous she was dating someone else.

Who most likely killed Hae Min Lee?

The person they've connected to her murder is a man that was named in the popular 'Serial' podcast: Ronald Lee Moore. "Serial" named Moore as a one-time suspect in the 1999 murder case of Hae Min Lee for which her ex-boyfriend Adnan Syed was found guilty.