Whose story doesn't add up? (v3)

"It’s been weeks. This is taking too long. We finally rounded up the
four suspects – the four people seen ducking into nearby shops right
around the time of death – got their statements and still don’t know
who the killer is. You were the first officer on the scene, right? You
said you were nearby and saw someone with baseball cap and green
clothes going in to the deli?"

"Right. And from other witnesses, we have that among the four, each
went into a different store: the deli, the pharmacy, the clothing
store and the grocer’s. Each had a different color of clothing: red,
green, blue and yellow. Each was carrying something different:
nothing, a shopping bag, a backpack and a briefcase. And each was
wearing a different hat: none, a baseball cap, a cowboy hat and a
beret."

"All we really have to go on are their hazy memories though.

Arden said, ‘I didn’t have a hat with me that day. … I don’t
remember where I was around that time, not the grocer’s though. … I
saw a couple other people walking around. One heading for the pharmacy
had a cowboy hat. The other was wearing green.’

Blair said, ‘I went to the grocer’s that day. … I remember seeing
someone with yellow clothes carrying a shopping bag, and someone with
a beret going in to the clothing store.’

Channing said, ‘I remember going to the clothing store. … I don’t
think I was carrying anything at the time. The only other person I saw
was carrying a briefcase into the pharmacy.’

Devon said ‘I wasn’t wearing red that day. … I saw someone with
empty hands. They weren’t wearing red either. … There was also
someone with a backpack and a baseball cap.’"

"That’s not much to go on, but it has to be one of them. They were the
only ones in the right place at the right time."

"Yeah. Something about this doesn’t add up though. Someone’s lying and
I have a feeling whoever it is is the killer."

Who is lying?

This is version 3. The first had no solution, and the second had two. Sorry about that. I’ve also taken other suggestions for improving the question in the process.