Police say significant DNA evidence links Arnis Zalkalns to the murder of Alice Gross and that investigators established enough to charge him, had he been alive.
Among the evidence was an iPhone cover found concealed in his garden.
Police said it was not possible to positively identify it by a reference to a serial number as it does not have one, but Alice's sister is confident it is hers.
The cause of Alice's death was "compressive asphyxia", police said. Zalkalns was found hanged in October last year, and police said they are not looking for anyone else in connection with the death.