Jonathan Laidlaw said today that UK prosecutors had produced "no smoking gun" to convict the former News of the World editor Brooks, who is accused of conspiring to hack phones, pay officials for information and obstruct a police investigation.
Seven people, including ex-tabloid editors Brooks and Andy Coulson, are on trial over wrongdoing at the now-defunct News of the World. All deny the charges.
Defense lawyers are making closing speeches at the long-running trial, which began in October. Judge John Saunders has told jurors he expects they will retire to consider their verdict on June 9.