It's The Ashes (again)

[backsidebaggie]

In this instance as well, Smith juggled the ball into his chest and held it against his chest, after the grass incident.

How exactly is he in control of the ball there?

That bit is irrelevant as it didn’t touch the ground during the juggle and he held it after that.

The key is did it touch the ground when he caught it and his hand hit the ground.

It is incredibly relevant. The umpire is judging that Smith had control of the ball, whilst the ball was probably touching the ground, so he judged it as a catch.

However, Smith had to maintain control of the ball throughout the process of the catch (see rule below), and the juggle clearly indicates that he didn't.

"33.3 Making a catch
The act of making a catch shall start from the time when the ball first comes into contact with a fielder’s person and shall end when a fielder obtains complete control over both the ball and his/her own movement."

Nope, if he ends with complete control, he can do keep ups, heads and volleys, anything he wants, as long as it ENDS with control and hasn’t touched the ground. The juggle is irrelevant. The only point in dispute is the earlier bit when it was borderline grounded.