On April 1, 1949, E. G. Robey opened the case for the prosecution before ten Sussex magistrates.  Haigh was present and he appeared to bask in the attention.  He took notes and made light banter throughout the proceedings, with no apparent awareness that his situation was quite serious.

G. R. F. Morris, Haigh's defense counsel, called no evidence during the two-day process.  He and the prosecution agreed to stick only to the Durand-Deacon case and to refrain from mentioning Haigh's statements about drinking his victims' blood.

For his part, Haigh envisioned a decade-long stint in a mental institution and then freedom to continue to prey on people.  He had seen the exaggerated newspaper accounts describing him as a blood-mad vampire and he was only too happy to go along.  As an added flourish, he once had drunk his own urine while in his cell.

Robey called thirty-three witnesses to prove premeditation of murder for gain.  He laid out his case in the form of a basic chronology that showed how rational Haigh's movements were:

Monday, Feb 14th, Haigh is in debt, with an unpaid hotel bill of fifty pounds.  He meets with Mrs. Durand-Deacon for lunch to offer a business proposition by showing her a box of plastic fingernails.

Tuesday: Haigh asks a local engineer at Crawley to fetch some acid from London.  He borrows fifty pounds from Mr. Jones, the managing director of Hurstlea Products, and tells him about the artificial fingernails.

Wednesday: Haigh pays his hotel bill with Mr. Jones' money.  He confirms his order for ten gallons of acid.

Thursday: The acid is delivered to Crawley.  Haigh gets a 40-gallon black drum from one company, and then exchanges it for a green one, prepared to resist corrosive acids.

Friday: Mrs. Durand-Deacon is seen carrying the handbag that is found later outside the storehouse in Crawley.  She is also seen by someone who recalls that she was wearing her Persian coat, and later that day, Haigh and Durand-Deacon drive away in his car.  She is not seen again.  At 4:45, Haigh tells Jones that the person he expected to meet regarding the fingernails has not shown up.

Saturday: Haigh tells Mrs. Lane that Durand-Deacon did not show up for their appointment.  That day he goes to Bull's to have some jewelry evaluated, but the licensed appraiser is out.  Another jeweler buys a wristwatch from Haigh, later identified by her sister as belonging to Mrs. Durand-Deacon.  Reigate cleaners also receives a Persian lamb coat, which is valued at about fifty pounds—the sum Haigh needs to repay his debt to Mr. Jones, now overdue.

Sunday, Feb 20, Haigh takes Mrs. Lane to the police station.

Monday: Haigh promises Jones a quick repayment of his debt.  He again takes jewelry to Messrs. Bull for valuation.  It is assessed at 131 pounds.

Tuesday: Haigh partly repays Mr. Jones what he owes.

Over the next few days, he adds money to his bank account, reducing an overdraft, and goes to pay Mr. Jones.  By then, Jones has been interviewed by the police and he urges Haigh to stay away.  Haigh continues to make statements professing his ignorance of Mrs. Durand-Deacon's whereabouts.

Saturday, February 26th: Sergeant Heslin breaks into the storehouse.  He finds a mackintosh, rubber gloves, a gas-mask case, a rubber apron, carboys that had contained sulfuric acid, and an acid-eroded stirrup-pump.  Sulfuric acid and animal fat are found on the gloves, mackintosh, and apron.  Human bloodstains are later found on the gas-mask case and apron.

Heslin also finds papers referring to other people who are missing, and a square case containing a revolver with eight rounds of ammunition; it has recently been fired.  In an attaché case is a receipt for a Persian lamb coat from a cleaner at Reigate.

Sunday: The coat is retrieved.

Monday: A bag found at the hotel where Mrs. Durand-Deacon lived contains portions of fabric that match patches on the bottom of the coat and left sleeve.

Inspector Symes collects the jewelry from Bulls'.  He brings Haigh to the police station, where he makes his lengthy and calculated confession.

Tuesday: Chief-Inspector Mahon goes to Crawley to take charge.  He also finds in Haigh's hotel room a shopping list that itemizes several things found in the Crawley storehouse.  He discovers a shirt with a bloodstained cuff.

Wednesday: Mahon finds a bloodstained penknife in the cubbyhole of Haigh's car.  Haigh is formally charged with murder.

Friday, March 2: Haigh makes a written statement that adds three more people to his list of six.

Tuesday, March 8: A chain and attaché case key that had belonged to Mrs. Durand-Deacon are found where Haigh said they would be.

Saturday, March 19: A handbag is found outside the Crawley storehouse that matches the handle pulled intact from the acid sludge.  It is the bag that others saw Mrs. Durand-Deacon carrying on Feb. 18th.  Inside are items identified as belonging to the victim.